Note - [image] indicates that there is a structure or figure at that point, all of which are present and generally looking just fine in the text copy that will make up the Abstract Book.
Also keep in mind that some Greek letters, subscripts, and other special characters may not have translated well to html.
(paper copy) means we will be xeroxing the abstract as submitted, usually due to the complexity of the structure and/or the absence of a file copy of the structure.
l. PHOTOCHEMISTRY IN SELF-ASSEMBLED MONOLAYERS. Marye Anne Fox, Chancellor, North Carolina State University, Raleigh, NC 27695.
Recent results will be discussed.
2. PI-SWITCHES: MULTI-STATE THERMAL AND PHOTOCHEMICAL SWITCHES DERIVED FROM DIMETHYLDIHYDROPYRENES. Reginald H. Mitchell*, Timothy R. Ward*, and Yunxia Wang, Department of Chemistry, University of Victoria, Victoria, BC V8W 2Y2.
Elaboration of the dimethyldihydropyrene - cyclophanediene
(DMDHP - CPD) photoswitch gives compound I, which has two distinct
photoisomers accessible from the ground state I. Results will
be presented.
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3. THE EMERGING CENTRALITY OF THE DIRECTED ORTHO METALATION REACTION IN SYNTHETIC AROMATIC CHEMISTRY. Victor Snieckus, Department of Chemistry, Queen's University, Kingston, Canada, K7L 3N6.
Recent developments in extensions and diversifications of Directed
ortho Metalation (DoM) have included connections to various
transition metal catalyzed cross coupling reactions. The discovery
of Directed remote Metalation (DreM) led to the generalization
of regiospecific strategies to fluorenones, highly substituted
biaryls, and polyaryls and polycondensed aromatic systems, and
some of their heteroaromatic analogues. Further extension has
been feasible to encompass DreM for the construction of substituted
thioxanthones, xanthones, acridones, and dibenzophosphorinones.
The Grubbs metathesis - DoM connection has allowed the synthesis
of aromatics annelated to large heteroatom-containing rings. Aspects
of these ongoing projects will be presented.
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4. SPIRO-PHENALENYLS: A NEW TWIST ON AN OLD IDEA. Robert C. Haddon, Departments of Chemistry and Physics, University of Kentucky, Lexington, KY 40506-0055.
We have previously reported the synthesis and solution properties of the spiro-phenalenyls [Tetrahedron 1986, 42, 6293]. These compounds show unusual electrochemistry, and we have provided evidence for an unusual mode of delocalization in these systems. I will discuss our latest results on the solid-state structures and electronic properties of these novel compounds.
5. SYSTEMATICS OF THE EXCITED STATES OF CYCLIC -ELECTRON SYSTEMS: AROMATIC TO ANTIAROMATIC UNDER ONE ROOF. Josef Michl*, Jörg Fleischhauer and Udo Höweler, Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309.
Recent developments in quantum chemistry permit accurate calculations of electronically excited states of conjugated molecules of respectable size. A complement to such calculations on individual molecules is provided by simple models that permit simultaneous treatment of whole classes of molecules, suggest rationalizations of excited state properties, and permit predictions of trends. A generalization of the classical perimeter model will be presented that permits the treatment of the electronic absorption and magnetic circular dichroism of electron systems derived from aromatic as well as antiaromatic perimeters with equal ease and brings to light the similarities as well as the profound differences between the electronic states of these two fundamental classes of cyclic conjugated molecules.
6. GEODESIC POLYARENES: RATIONAL SYNTHESES AND NOVEL PROPERTIES. Lawrence T. Scott*, Dorin V. Preda, Ronald B. M. Ansems, and Hindy E. Bronstein, Department of Chemistry, Boston College, Chestnut Hill, MA 02467-3860.
(paper copy)
7. TETRATHIAFULVALENOPHANES AS NOVEL ELECTRON DONORS. Tetsuo Otsubo, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima, 739-8527, Japan.
(paper copy)
8. NANOPOROUS MATERIALS FOR INTERLAYER DIELECTRICS IN ULSI DEVICES. C. Pan, B. L. Sun, J. N. Cox, and C. Chiang, Intel Corporation, Components Research, 3065 Bowers Avenue, Santa Clara, CA 95052.
An interlayer dielectric (ILD) thin film with a reduced dielectric constant (k) can improve interconnect performance in ULSI devices by reducing signal delay within and cross-talk between the metal lines it separates. The dielectric constant is 4 for silica, which is widely used as ILD currently, 3-4 for fluorinated silica, 2-3 for organic polymers and organosilane, 1.5-2 for porous organic polymers and silica, and k~1 for air. Our primary interest here is nanoporous silica and organic polymers. A major challenge for using nanoporous materials as ILD is mechanical strength. Various chemical structures have been engineered and film deposition processes have been developed to improve the mechanical strength of the materials. One order of magnitude increase in modulus has been achieved. The ultimate goal is to understand the relationship between property and chemical structure and to engineer promising materials as low k ILD.
9. ASSEMBLY OF NANOPARTICLES ON BIOMOLECULAR SCAFFOLDS: THE INFLUENCE OF POLYPEPTIDE SCAFFOLDS ON ASSEMBLY STABILITY AND THE CHARACTERISTICS OF ELECTRON TRANSPORT. Laura Clarke**, Martin N. Wybourne**, Jana Mooster, Leif O. Brown, Scott M. Reed, and James E. Hutchison*, Department of Chemistry, University of Oregon, Eugene, OR 97403-1253 and **Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755.
The novel electronic properties (e.g., Coulomb blockade) of nanometer scale assemblies of metal nanoparticles make them potentially useful in nanoelectronic devices and extremely sensitive chemosensors. To date, no straightforward and reproducible methods are available for the fabrication of low-dimensional nanoparticle assemblies. Our method of nanofabrication involves the assembly of functionalized metal nanoparticles onto rigid biomolecular scaffolds on an insulating substrate. Our previous investigations of unpatterned nanoparticle thin films provided clear evidence of Coulomb blockade at room temperature, but the response was unstable over time. In this paper we present results for two-dimensional arrays of gold nanoparticles assembled onto a poly-L-lysine scaffold layer. The assembly process provides a simple, chemical method to immobilize the particles and thus stabilize the electrical response (Coulomb blockade) of the array. In addition to stabilizing the array, the polypeptide scaffold is found to mediate one-dimensional electron transport through the film.
10. BIOMOLECULAR TEMPLATING OF GOLD NANOPARTICLES. Scott M. Reed*, Walter W. Weare, Leif O. Brown, Marvin G. Warner, and James E. Hutchison*, Department of Chemistry, University of Oregon, Eugene, OR 97403-1253
Assembly of functional electronic devices on the nanometer scale will require the development of new methodologies for assembly. In our approach, biological molecules with well understood self-assembly are used as templates for the design of nanoelectronic devices. Our synthesis of 1.4 nm gold nanoparticles passivated with alkanethiols has already been described. Here we will present methods of incorporating organic molecules that have a known affinity for biomolecules into the passivating shell of gold nanoparticles. The terminal functionalizations of these thiols are ligands that are known to have an affinity for specific biomolecules. In one case, a known DNA intercalant is incorporated into the ligand shell. In another case, a nitrilotriacetic acid functionality is incorporated into the ligand shell enabling site specific binding to histidine residues in proteins. These functionalized nanoparticles and the resultant assemblies are analyzed by a variety of surface techniques including TEM, AFM and X-ray Photoelectron Spectroscopy.
11. SELF-ASSEMBLED MONOLAYERS ON MESOPOROUS SUPPORTS: SYNTHESIS OF NANOSCALE HYBRID MATERIALS AND THEIR APPLICATIONS. Glen E. Fryxell,* Jun Liu, Tom S. Zemanian, Teresa A. Hauser, James A. Franz, Kentin Alford, Li-Quong Wang; Pacific Northwest National Laboratories, P.O. Box 999, Richland, WA 99352.
The advent of mesoporous ceramics has provided rapid access to readily manipulated, high surface area supports, in which the porosity is both open and accessible. We have chosen to use these materials as a foundation upon which to build terminally functionalized self-assembled monolayers, thereby creating an ordered molecular hierarchy. This 3-dimensional molecular architecture can provide a highly uniform chemical interface, of extremely high surface area. The nuances of these syntheses will be discussed, as will certain applications of these nanoscale hybrid materials as environmental sorbents.
12. ATOMIC LAYER EPITAXY OF Ta2O5-BASED COMPOSITE THIN FILMS AS GATE DIELECTRICS. Hui Zhang, Douglas Skinner and Raj Solanki*. Department of Electrical and Computer Engineering, Oregon Graduate Institute of Science and Technology, Portland, Oregon 97291.
Atomic layer epitaxy (ALE) as a self-limiting thin film growth process can be used to produce ultra thin films on large areas with good conformality and reproducibility. The self-controlling feature of ALE allows us to grow multilayer structures of dielectric thin films at low temperatures in a continuous process. In this paper the use of ALE in deposition of Ta2O5, HfO2, ZrO2 thin films and their nanolaminates on silicon substrates at 300oC will be presented. Metal-chlorides and water were used as precursors. Material (TEM, x-ray) and electrical (dielectric constant, leakage current) properties of these films were evaluated.
13. FORMATION OF SUB-MICRON SCALE FEATURES USING COPPER ELECTRO-DEPOSITION. Jonathan D. Reid, Novellus Systems. 26277 SW 95th Ave, Wilsonville, OR 97070.
Copper is now widely accepted as the interconnect material of choice in future integrated circuit device generations. A preferred method for interconnect feature formation utilizes copper electrodeposition onto thin copper layers previously formed by vapor deposition processes. Complete void free filling of features which may be 5-10 times deeper than they are wide presents a significant challenge to traditional electroplating technology. In order to avoid pinch-off and subsequent void formation, an electrodeposition process must proceed at a rate near the base of the features which is accelerated to several times the rate of deposition at the top of the features. Such behavior has been achieved using classical copper sulfate/sulfuric acid plating solutions in which the rate of deposition is controlled as a function of geometric location by selective adsorption of organic molecules. This paper describes classes of molecules with catalytic and inhibitory effects on the deposition process which may be added at specific concentrations to electroplating solutions to enable filling of 0.12 micron width, 9:1 aspect ratio features. The effect on filling of various factors including organic species and cupric ion diffusion rates and concentrations, temperature, current density and waveform., and agitation will be discussed.
14. RECENT DEVELOPMENTS IN THIN FILM INTERFACE ADHESION MEASUREMENT TECHNIQUES. Tracey Scherban, Safaa El-Mansy*, Milt Jaehnig, Intel Corporation, Hillsboro, Oregon, Brad Sun, Qing Ma, Quan Tran, Intel Corporation, Santa Clara, California and Jose M. Sanchez, Reyes Elizalde, CEIT, San Sebastian, Spain.
The mechanical integrity of thin film interfaces is of critical
importance to semiconductor device reliability. Strong interfaces
are required to prevent thin film delamination which can lead
to electrical failure. This paper reviews new techniques developed
to better characterize thin film interface adhesion strength.
These techniques represent a significant improvement over previous
methods, such as the tape test. Four point bending is a quantitative
technique in which a sandwich structure is loaded in flexure,
resulting in crack propagation to weak interfaces. Cross-sectional
nano-indentation (CSI) is a quick, qualitative technique to assess
delamination based on interaction of indentation cracks with thin
film interfaces. The chemistry of the interface can strongly modulate
the mechanical strength. The use of surface chemical analysis
techniques, such as X-ray Photoelectron Spectroscopy (XPS), in
conjunction with mechanical measurement techniques, represents
a powerful tool in understanding and optimizing thin film interface
properties. Recent adhesion results for multilayer structures
consisting of dielectric thin films will be reviewed.
15. SPECTROSCOPIC ELLIPSOMETRY AS A PROBE FOR THE MICROSTRUCTURE
OF POROUS THIN FILMS. H. Zhang, Department of Electrical and
Computer Engineering, Oregon Graduate Institute, Beaverton, OR
97006, and J. Neal Cox*, Components Research, Intel Corp., Hillsboro,
OR 97124.
Spectroscopic Ellipsometry (SE) is used routinely to determine thicknesses and optical properties of thin films. Application to the SE data of more detailed models provides with varying degrees of success details about the microstructure of inhomogeneous, porous films. For one film type, SE revealed a moderate density of micrometer-scale voids. A model of surface roughness was consistent with the rupturing of these voids to the surface. For a series of polyimide films prepared with varying densities, the modelling of the SE data was more ambiguous. Nevertheless, trends in the SE data were observed and progress on the development of a comprehensive model are discussed. For "nanoporous" films, which supposedly contain very high densities of nanometer-scale voids, the SE data is best represented by models of homogeneous films with well-behaved optical properties that differ from that of their non-nanoporous counterparts.
16. RAMAN SPECTROSCOPY: A UNIQUE METHOD FOR PROCESS CONTROL. Mike Carrabba*, Steve Barnett, Rick Bormett* and Mark Pavlosky*, Renishaw, Inc. 623 Cooper Ct., Schaumburg, IL 60173.
Raman spectroscopy can be used to identify and quantify molecules via their characteristic vibrational signatures. For many years the Raman technique has been mainly used in the research laboratory. With the recent advances in charge coupled device (CCD) detectors, optical filters, diode lasers, and fiber optics, Raman spectroscopy has started to become a reliable method for process control. This paper will review the Raman technique and describe the use of Raman spectroscopy for the control and management of industrial processes.
17. REAGENT-BASED OPTICAL CHEMICAL SENSORS: REAL WORLD POTENTIAL AND PERFORMANCE. Michael D. DeGrandpre* and Matthew M. Baehr, Department of Chemistry, The University of Montana, Missoula, MT 59812.
An enormous amount of research has been devoted to the development of optical chemical sensors over the past 15-20 years. One group of sensors within this category, reagent-based optical chemical sensors, or ROCS, has not met with widespread commercial success, largely due to drift problems and inconsistent sensor-to-sensor behavior. If these limitations could be overcome, ROCS could operate without the need for calibration - a highly desirable, but as of yet unattainable goal. Our work has focused on the development of ROCS for autonomous in situ measurements of seawater pCO2 (partial pressure of CO2), an application where it is very difficult to perform periodic calibrations. The pCO2 sensor developed from this work has demonstrated exceptional long-term stability and the performance characteristics suggest that calibrations could become unnecessary. We show through response comparisons of identically-designed sensors and long-term studies that calibration-free operation is indeed feasible. The theoretical response, determined from thermodynamic characterization of the indicator solution, also predicts the observed calibration-free performance. Other absorbance-based sensors, such as optrodes, can be designed and operated in a similar fashion, making calibration-free ROCS available for a wide range of industrial, biomedical and environmental applications.
18. ANALOG CHEMOMETRICS: NEW METHODS FOR IMPROVING OLD SENSORS. Karl S. Booksh* and Marc K. Boysworth, Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287.
Propagation of errors theory states that in the extreme cases of poor signal to noise or high spectral overlap, employment of digitized spectra for multivariate regression is not optimal for minimizing errors in analyte quantitation. In the particular with scanning and filter-wheel spectrometers, digitization of entire spectra results in a distribution of errors across each spectrum that is independent of the importance of each digitized wavelength for determination of analyte concentration. The errors imbedded in each digitized channel are hence magnified during multiplication of the digitized spectrum with the previously calculated regression vector; there is no assurance that the channels with the best signal to noise will also be the most important channels for regression. With instrumental responses containing errors that are predominantly independent of signal intensity, the error of quantitation can be statistically reduced by adjusting the scanning rate at each wavelength to mimic the relative importance of the wavelength for multivariate regression will integrating the detector throughout the entire scan. This, in effect, performs an analog computation of the dot product of the spectrum with the regression vector on the detector. The benefits of such "analog regression" and its extension of "analog variable selection" will be demonstrated with data collected from a fiber optic, acousto-optic tunable filter based spectrometer and supported by Monte Carlo simulations.
19. COST EFFECTIVE LIQUID CHROMATOGRAPHY THROUGH WATER MOBILE PHASE AND MICROFABRICATED INSTRUMENTATION. Paul G. Vahey and Robert E. Synovec*, Department. of Chemistry, University of Washington, Seattle, WA 98195.
The development of cost effective instrumentation and methodology for process liquid chromatography is reported. The use of a 100% water mobile phase is a departure from current reversed phase liquid chromatography (RP-LC), which usually involves organic solvents. Analysis times and selectivities can be comparable traditional RP-LC separations which employ a C18 stationary phase, with an organic solvent modified mobile phase. Unique advantages result from the low background signal of water in absorbance, Raman, and conductivity detection. A new direction in cost-effective chromatography is microfabricating chromatographic devices. A rapid prototyping technique known as soft lithography, is used to create channels 100 µm wide by 10 µm deep. At these dimensions, high separation efficiencies can be achieved with operating pressures below 5 psi, and solvent consumption under 2.5 mL per week. Current research is focused on modifying channel surfaces and developing on-column detection, to broaden the scope of applications.
20. LIQUID CHROMATOGRAPHY WITH A WATER MOBILE PHASE COUPLED TO HIGH-SPEED CAPILLARY GAS CHROMATOGRAPHY. Wes C. Quigley*, Carlos G. Fraga, and Robert E. Synovec*, Department of Chemistry, University of Washington, Seattle, WA 98195.
A chemical analyzer will be reported based upon coupling liquid chromatography (LC) with a water mobile phase via a novel interface to high-speed capillary gas chromatography (GC). The interface preserves the temporal information of the LC separation, thus a comprehensive two-dimensional LC x GC separation is obtained. LC usually requires organic solvent mobile phase modifiers, so the current work is a departure from typical practice of LC due to the 100% water mobile phase. Separations of a wide variety of compounds have been achieved. A water mobile phase simplifies instrumental requirements, thus enhancing separation and detection strategies. This broadens the scope of LC to on-line process analysis and field monitoring applications by improving safety and minimizing waste. Combining this analyzer with chemometric analysis will be explored.
21. THE USE OF RAMAN SPECTROSCOPY AS A DETECTOR FOR LIQUID CHROMATOGRAPHY. Brian J. Marquardt and Lloyd W. Burgess*, Center for Process Analytical Chemistry, University of Washington, Seattle, WA 98195.
Historically, Raman spectroscopy has not been widely used for process analysis for a variety of reasons, mainly its lack of sensitivity. In this presentation, we will discuss our efforts to effectively develop a highly sensitive Raman detector for liquid chromatography (LC). An inline Raman detection cell has been developed for LC analysis and it is compatible with the typical elution volumes of capillary LC. The detection cell greatly enhances the sensitivity of a typical Raman measurement without resorting to surface enhancement or resonance approaches. By coupling the separation achieved in a liquid chromatogram with the vibrational information gleaned from Raman detection, one can more easily deconvolute and identify individual chemical species in a complicated sample matrix. The resultant, relatively fast, selective and sensitive analysis allows for the collection of information rich multivariate data.
22. OPTICAL LOW COHERENCE REFLECTOMETER FOR PROCESS CONTROL. Simonida R. Thurber, Paul H. Shelley*, Anatol Brodsky, and Lloyd W. Burgess*, Center for Process Analytical Chemistry, University of Washington, Seattle, WA 98195-1700.
Optical Low Coherence Reflectometer is a test and measurement instrument used in the optical communications industry. It uses single mode fibers as both the test probe (fixed mirror equivalent) and reference (moving mirror equivalent) legs of a fiber optic Michelson interferometer. The optical design is based on low coherence (broad bandwidth) light that results in a nominal peak width of 10 microns for a discrete reflection of the 1.3 micron source beam. The Reflectometer has been investigated for a number of potential material analysis applications at the Center for Process Analytical Chemistry (CPAC). The studies include: thickness measurements of components within multiple layer polymer films, simultaneous thickness and refractive index measurements of clear coatings, determination of thickness of highly scattering coatings on both conducting and non-conducting materials, monitoring of paint curing, and scattering in dense liquid suspensions, including the on-line determination of the "degree of doneness" in an attrition milling process (without dilution).
23. SINGLE FIBER KAPPA NUMBER ANALYZER. Carstern Bruckner*, John Robinson, Kuntinee Suvarnakich, Richard Gustafson*, and James Callis*, Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700.
An on-line epi-fluorescence optical instrument has been designed to measure the lignin content of individual wood fibers at high rates of speed for a pulping process. The instrument will be able to measure the heterogeneity of the pulp; such information can greatly assist in process optimization. The current Kappa Number Test, which measures lignin content, is time consuming and only determines an average kappa number over a large population. Our new method correlates kappa number with fiber fluorescence. Acridine Orange is bound to wood fibers. Fiber fluorescence is green at low kappa numbers, and becomes red as lignin content increases. An image acquisition and analysis package has been developed to quantify the fiber fluorescence measured with two CCD cameras, one of which measures the green fluorescence, and the other the red. By taking the ratio of red to green fluorescence, we obtain an index that can be correlated with kappa number.
24. MEASUREMENT OF THE MATERIAL DEPENDENCE OF ELECTRON TRANSFER UPON PEPTIDE MATERIAL. Robert S. Clegg and James E. Hutchison*, Department of Chemistry and Materials Science Institute, University of Oregon, Eugene, OR 97403-1253.
The role of proteins as molecular spacers in photosynthesis and mitochondrial respiration makes the dependence of electron transfer (ET) on the intervening medium an important problem. Others have measured the heterogeneous ET rate constant ket across alkanethiol self-assembled monolayers (SAMs) on metal electrodes. We have developed well-ordered, peptide-containing SAMs and have measured ET kinetics across the peptide spacers. Using a battery of characterization methods, methyl-terminated SAMs containing one, two and three amide groups per precursor and hydrophobic alkyl "tails" are demonstrated to be well ordered; thus, a single ET process should predominate in the kinetic measurement. Formation of mixed SAMs containing analogous electroactive precursors having terminal ferrocenecarboxamide groups leads to electrochemically reversible cyclic voltammetry (fwhm £ 96 mV) and chronoamperometry (single exponential current decay), allowing calculation of ket for amide material by independent methods. The ET decay constant b for this model system supports the "preferred pathways" model of ET.
25. ANALYSIS OF PROTEIN-DNA PHOTOCROSSLINKS BY MATRIX-ASSISTED LASER DESORPTION/IONIZATION MASS SPECTROMETRY AND ELECTROSPRAY IONIZATION TANDEM MASS SPECTROMETRY. Douglas F. Barofsky* and Philip R. Gafken, Department of Chemistry, Oregon State University, Corvallis, OR 97331-4003.
Proteins interact with DNA during replication, transcription, recombination, and DNA repair. Identifying the sites of protein-DNA contact within the complex formed during such an interaction is important to understanding the mechanism of the protein's biological function within the cell. We are presently developing a general protocol for probing protein-DNA interfaces that involves purification and mass spectrometric analysis of the nucleopeptide-products of a tryptically digested UV-crosslinked protein-nucleic acid complex. The purified heteroconjugates are in a form that can be readily analyzed by matrix-assisted laser desorption/ionization mass spectrometry and electrospray ionization tandem mass spectrometry to identify the crosslinked amino acids. The protocol is straightforward, reproducible, and should be applicable to the study of many DNA binding proteins. Our presentation will illustrate the application of our protocol to E. Coli uracil-DNA glycosylase photocrosslinked to polydeoxythymidylate.
26. TWO NOVEL METHODS FOR SOLID-PHASE SYNTHESIS OF DNA INTERSTRAND CROSS-LINKS - SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF A NITROUS ACID INTERSTRAND CROSS-LINKED DUPLEX DNA. Eric A. Harwood, Snorri Th. Sigurdsson*, N. B. Fredrik Edfeldt, Brian R. Reid and Paul B. Hopkins*, Department of Chemistry, University of Washington, Seattle, WA 98195-1700.
Nitrous acid promotes the formation of interstrand cross-links in duplex DNA. The cross-link lesion consists of two 2'-deoxyguanosines sharing a common N2 atom (1). Investigation of the structure of nitrous acid cross-linked DNA requires a homogenous sample, not attainable by treatment of duplex DNA with aqueous nitrous acid. We report two new methods for the solid-phase synthesis of interstrand cross-linked DNA and their application for preparation of nitrous acid cross-linked duplex DNA. Phosphoramidite derivatives of 1 were synthesized for both of these methods. The first method required coupling of a mono-phosphoramidite to a single oligonucleotide chain followed by inverse DNA synthesis. In the second strategy, a bis-phosphoramidite was coupled directly to two oligonucleotide chains. The latter strategy was used to synthesize a nitrous acid interstrand cross-linked duplex DNA for structural analysis by 1H-NMR. Initial results of these structural studies are discussed. The synthetic strategy described should be applicable for the synthesis of other cross-linked oligonucleotides as well.
27. DYNAMICS OF NEUROPHYSIN BY 1H NMR AMIDE HYDROGEN EXCHANGE. Ayna N. Alfadhli and David H. Peyton*, Department of Chemistry, Portland State University, Portland, OR 97207-0751.
The neurophysins are homodimeric proteins that exhibit thermodynamic linkage between dimerization and their biological function, the binding of peptide hormones oxytocin and vasopressin. Recent studies have shown that in the neurophysin-hormone precursor, mutation of neurophysin causes diabetes insipidus disease. This disease seems to arises from neurophysin's misfolding. Characterization of neurophysin backbone dynamics is needed to delineate regions that play essential roles in folding and, therefore dictate protein function. Here, we report the analysis of the hydrogen exchange experiments on neurophysin monomer. Our results suggest that the C-domain core of the protein is the folding core of neurophysin, and may be considered as part of an early folding nucleus. The results were verified by the refined NMR solution state structure of the neurophysin's C-domain..
28. AN H-D EXCHANGE STUDY TO TEST THE NUCLEOPHILICITY OF THE BOUND SUBSTRATE IN OXIDATION OF 2,5-DIHYDROXYACETANILIDE BY AN ENZYME FROM STREPTOMYCES MPP3051. Ana C. Barrios and Kevin P. Gable*, Department of Chemistry, Oregon State University, Corvallis, OR 97330.
Dihydroxyacetanilide Epoxidase II from S. MPP3051 has been postulated to operate via a mechanism involving nucleophilic attack of deprotonated, bound substrate on molecular O2. H-D exchange studies reveal that chemical exchange with solvent (water) occurs only under strongly acidic conditions, and that enzymatic exchange at pH 6.5 does not occur. Although not unequivocal proof, these results agree with an alternative mechanism involving one-electron transfer and the intermediacy of superoxide.
29. HAMMETT STUDY ON COMPETITIVE INHIBITORS OF DIHYDROXYACETANILIDE EPOXIDASE I AND II. Kevin P. Gable* and Scott E. Allen, Department. of Chemistry, Oregon State University, Corvallis, OR 97330-4003.
Dihydroxyacetanilide Epoxidase (DHAE) I and II, both dioxygenases,
catalyze the conversion of 2,5-dihydroxyacetanilide, 1,
into epoxyquinones 2a or 2b. DHAE I and II are unique
in that no co-factors are required and enantiomeric products are
formed. A series of substituted benzanilides, with a range of
Hammett substituent constants, was synthesized and tested as competitive
inhibitors of DHAE I and II. From these results, the data suggests
that the carbonyl of the amide bond is involved in binding to
the active site of DHAE I, whereas in DHAE II the carbonyl does
not appear to be involved.
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30. OXIDATION OF PHENOLS BY TYROSINASE: SUBSTITUENT AND DEUTERIUM ISOTOPE EFFECTS. Amrita K. Sahota#, Erik Mork*, Matthew S. Dowling#, Kenneth G. Strothkamp*#, *Department of Chemistry, Lewis and Clark College, Portland, OR 97219 and #Department of Chemistry, Reed College, Portland, OR 97202.
Initial rate studies of the oxidation of a variety of phenols were employed to investigate the tyrosinase mechanism. The effects of m- and p-substitution on the kinetic constants of the reaction were determined. The ability of a phenol to serve as a substrate correlates with the pKa < 9 are competitive inhibitors. A solvent deuterium isotope effect was observed in the oxidation of several phenols, including L-tyrosine. These results indicate that proton transfer from the phenolic hydroxyl is at least partially rate limiting, consistent with the proposal of hydroxyl proton transfer in the tyrosinase mechanism (Biochemistry, 1994, 33, 5730). A small isotope effect was noted in the oxidation of 2,4-dideuterio-L-tyrosine. This suggests that, for L-tyrosine, C-H bond cleavage also affects the kinetics.
31. AQUEOUS CHEMISTRY OF MOLYBDENOCENE DICHLORIDE. Louis Y. Kuo*, Nicholas M. Perera, Laurie Barnes, Christoph Balzarek, and David R. Tyler, Department of Chemistry, Lewis and Clark College*, Portland, OR 97219 and Department of Chemistry, University of Oregon, Eugene OR 97403.
We present an overview of our work on applying the metallocene bis(h5-cyclopentadienyl) molybdenum dichloride organometallic (Cp2MoCl2: Cp = h5-C5H5) towards hydrolyzing organo phosphates in aqueous solution. Cp2MoCl2 readily dissolves in water by losing both chlorides to yield an aquated species that retains the Cp-Mo ligation. This species hydrolyzes activated and unactivated phosphate esters with rate accelerations of 108 for p-nitrophenylphosphate and 104 for dimethyl phosphate. The half-order dependence in Cp2MoCl2(aq) seen for these processes suggests there is a monomer-dimer pre-equilibrium and that the active hydrolytic species is the monomer. An extension of this work involves using Cp2MoCl2(aq) towards hydrolyzing phosphate triesters such as the pesticides parathion and paraoxon (pH 3 and 7). In both cases we see clear evidence for hydrolysis that results from either C-O (parathion + Cp2MoCl2) or P-O bond cleavage O (paraoxon + Cp2MoCl2) that uses water/hydroxide as the nucleophile.
32. THIOPHOSPHATE HYDROLYSIS BY MOLYBDENOCENE DICHLORIDE. Nicholas M. Perera and Louis Y. Kuo*, Department of Chemistry, Lewis and Clark College, Portland, OR 97219.
The pesticides parathion and paraoxon are biochemically similar to many neurotoxins. NMR spectral evidence suggest that bis(h5-cyclopentadienyl) molybdenum (IV) dichloride (Cp2MoC12: Cp = h5-C5H5) degrades parathion and paraoxon via a hydrolytic pathway. This is the first case of an organometallic compound that hydrolyzes organophosphate pesticides in aqueous solution. Cp2MoC12 promotes hydrolytic phosphotriester bond cleavage in paraoxon with rate accelerations of >103 and >106 at pD3 and pD7, respectively. This hydrolysis involves a nucleophilic attack by water or hydroxide onto the phosphorus center (P-O bond cleavage) to yield p-nitrophenol and diethyl phosphoric acid. The DS of activation for this paraoxon hydrolysis is -50 e.u. which suggests an intermolecular pathway. Cp2MoC12 promotes the hydrolytic C-O bond cleavage in parathion with a rate acceleration of 10 at pD7. The hydrolysis of parathion involves a nucleophilic attack by water or hydroxide, but onto carbon instead of phosphorus to yield ethanol and deethyl parathion.
33. FLUORINATED AMIDO COMPLEXES OF ZIRCONIUM AND YTTRIUM. David J. Berg*, Katherine Burrage, and Sheryl Steeves, Department of Chemistry, University of Victoria, P.O. Box 3065, Victoria, BC, Canada V8W 3V6.
The synthesis of a series of fluorinated amide ligands (1)
and their zirconium (2) and yttrium complexes (3)
will be presented. The increased Lewis acidity at the metal center
makes complexes typified by 2 excellent Lewis acid catalysts
for reactions such as the Meerwein-Pondorff-Verley reduction,
nitroaldol condensation and hetero Diels-Alder cyclization. Chiral
derivatives of 2 have been prepared and preliminary efforts
to use these as asymmetric Lewis acid catalysts will be discussed.
Organometallic complexes such as 3 display increased alkene,
CO and isocyanide insertion chemistry into the metal-carbon bond
when compared to non-fluorinated analogues. In addition, the fluorinated
complexes all display significantly enhanced solubility in hydrocarbons
over non-fluorinated analogues.
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34. OXIDATIVE ADDITION AND REDUCTIVE ELIMINATION REACTIONS AT Pt(II)/Pt(IV). Karen I. Goldberg, Department of Chemistry, University of Washington, Seattle, WA 98195-1700.
The oxidative addition of a carbon-hydrogen bond to a Pt(II) center has been proposed as the substrate activation step in Pt-catalyzed reactions which functionalize alkanes. Reductive elimination from Pt(IV) to form a carbon-heteroatom bond has been proposed as the product release step. We have been able to directly observe and study these and related oxidative addition/reductive elimination reactions with model Pt(II)/Pt(IV) complexes. Kinetic and mechanistic studies of the reactions will be presented with primary emphasis on the formation and cleavage of carbon-hydrogen, carbon-carbon and carbon-oxygen bonds.
35. RECENT ADVANCES IN COMPUTATIONAL CHEMISTRY: NEW METHODS AND APPLICATIONS TO CATALYSIS, MATERIALS AND BIOCHEMISTRY. William A. Goddard, III, Charles and Mary Ferkel Professor of Chemistry and Applied Physics, Director, Materials and Process Simulation Center (MSC), California Institute of Technology (139-74), Pasadena, CA 91125.
We will summarize recent advances in atomistic simulations
involving: quantum chemistry, force fields, and molecular dynamics
with applications involving chemistry, materials science, and
biochemistry. Topics to be covered will be selected from:
Homogeneous polymerization catalysts
Catalytic activation of small alkanes
Chemisorption and rearrangement of hydrocarbons on noble metal
surfaces
Protein folding
Organic chelants for radio-cancer therapy
First principles modeling of gasoline refinery kinetics
Structures and properties of dendritic polymers
Structure and properties of single-wall carbon nanotube ropes
Shock-induced phase transitions in ceramics
Plasticity of metal alloy nanotubes
Reconstruction of GaN surfaces
Wear inhibitors for automobile engines
Scale inhibitors and wax inhibitors for oil pipelines
Melting and glass transformations of metal alloys.
36. ACCURATE THEMOCHEMISTRY VIA LOCAL MULTIREFERENCE PSEUDO-SPECTRAL
CORRELATION METHODS. Robert B. Murphy*, Schrödinger,
Inc., 121 S.W. Morrison Ave., Portland, OR 97204 and Barry Dunietz
and Richard A. Friesner, Department of Chemistry, Columbia University,
New York, NY 10027.
We have developed an accurate method for thermochemical calculations based upon single and multi-reference local MP2 methods, LMP2 and GVB-LMP2. In analogy to G2 theory the method uses empirical correlation corrections partitioned into sigma and pi contributions. The pseudospectral correlation methods of this theory have a very favorable cubic scaling with system size allowing applications on systems as large as a carbon C20 cluster with large triple zeta basis sets. Results for heats of formations of molecules in the larger G2 test suite will be presented as well as a study of C20 isomers in comparison to density functional theory.
37. IMPROVED ACCURACY WITH RECENT DENSITY FUNCTIONALS. Mark Stave and James Anchell, Oxford Molecular Group, 14940 NW Greenbrier Parkway, Beaverton, OR 97006-5733.
A number of recently published studies [1,2] describe the development
of new exchange-correlation energy density functionals that depend
only on the electron charge density and its gradient and, thus,
fall within the generalized gradient approximation (GGA). These
new functionals enable molecular property predictions that are
at least as accurate as those based on hybrid functionals [3],
such as B3LYP [4], without introducing any fraction of exact orbital
exchange. Consequently, computations involving these new GGA functionals
are much faster than those using the hybrid functionals. We report
results from calculations using two of these new functionals as
implemented in the DGauss density functional program.
[1] M. Filatov and W. Thiel, Molec. Phys. 91, 847 (1997).
[2] F. A. Hamprecht, A. J. Cohen, D. J. Tozer and N. C. Handy,
J. Chem. Phys. (submitted).
[3] A. D. Becke, J. Chem. Phys. 98, 5648 (1993).
[4] P. J. Stephens, F. J. Devlin, C. F. Chabalowski, and M. J.
Frisch, J. Phys. Chem. 98, 11623 (1994).
38. THE IMPORTANCE OF STATIC CORRELATION IN THE BAND STRUCTURE OF HIGH TEMPERATURE SUPERCONDUCTORS. Jason K. Perry, First Principles Research, Inc., and Schrödinger, Inc., 8391 Beverly Blvd., #171, Los Angeles, CA 90048.
Recently we presented a new band structure for La2-xSrxCuO4 and other high temperature superconductors in which a second narrow band was seen to cross the primary band at the Fermi level. The existence of this second Fermi level band is in complete disagreement with the commonly accepted LDA band structure. Yet it provided a crucial piece of physics which led to an explanation for superconductivity and other unusual phenomena in these materials. In this work we present details as to the nature of the failure of conventional methods in deriving the band structure of the cuprates. In particular, we use a number of chemical analogues to describe the problem of static correlation in the band structure calculations and show how this can be corrected with the predictable outcome of a Fermi level band crossing. A preprint of this work may be downloaded from xxx.lanl.gov/abs/cond-mat/9903088.
39. CORRELATION-CONSISTENT BASIS SETS FOR THE NICKEL ATOM. Douglas L. Strout and Thom H. Dunning, Jr.*, Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, MS K1-96, Richland, WA 99352.
Following the techniques previously applied to main group elements, correlation-consistent basis sets are developed for the nickel atom. Basis sets of double zeta (DZ) to sextuple zeta (6Z) quality are built up by the addition of groups of basis functions based on each function's contribution to the total energy. Benchmark calculations are carried out on the atomic state splittings and electron affinity. Bond lengths, frequencies, dissociation energies, and electron affinities are calculated for nickel-containing diatomics. Coupled-cluster theory (CCSD(T)) is shown to give good results, and relativistic effects are shown to be important.
40. APPLICATION OF NATURAL BOND ORDER ANALYSIS AND NATURAL RESONANCE THEORY TO THE STABILITY AND REACTIVITY OF PEROXYNITROUS ACID CONFORMERS. Bryant A. Gilbert, Department of Chemistry, Portland State University, Portland, OR 97207-0751.
[image]
The nitration and oxidation chemistry of peroxynitrous acid is currently interpreted in terms of the stability of its cis (1) and trans (2) conformations. The results of Natural Bond Order Analysis (NBO) and Natural Resonance Theory (NRT) are used to define the electronic factors responsible for this stability/reactivity relationship. A unified mechanism will be provided which accounts for the nitration and oxidation chemistry of peroxynitrous acid in terms of acid-base chemistry.
41. TRAJECTORY STUDIES OF OH + O COLLISIONS: QUENCHING OF VIBRATIONALLY EXCITED OH. Robert J. Hinde, Department of Chemistry, University of Tennessee, Knoxville, TN 37996-1600.
The chemical heating rate of the terrestrial mesosphere is highly sensitive to the rate at which vibrationally excited OH radicals are quenched in collisions with oxygen atoms. However, quenching rate constants for OH (v) + O collisions have not been measured experimentally for v > 1. We present the results of a quasiclassical trajectory study of OH (v) + O quenching collisions and use these results to estimate the quenching rate constants for highly excited (v > 1) OH radicals. We also comment on the role which inelastic OH (v) + O collisions may play in producing the vibrationally cold, rotationally hot OH radicals that have recently been observed in the mesosphere.
42. UV/VIS MULTIPHOTON DISSOCIATION DYNAMICS OF CHROMIUM CARBONYL COMPLEXES. Daniel P. Gerrity, Department of Chemistry, Reed College, Portland, OR 97202.
The UV/visible laser multiphoton dissociation (MPD) of vapor-phase organometallics produces neutral metal atoms in both ground and excited states. We use spontaneous and laser-induced fluorescence techniques to measure the relative product state distribution of the electronic states of atomic Cr produced in the MPD of several chromium carbonyl compounds. The dependence of this distribution on photodissociation wavelength, laser power, ligand complexity, and added buffer gas pressure is being used to explore the dynamics of the MPD process. Evidence will be given for the existence of non-statistical dissociation pathways, and recent work on the effect of added buffer gas pressure on the chromium atom product state distribution will be described.
43. A TIME-RESOLVED RESONANCE RAMAN STUDY OF CHLORINE DIOXIDE PHOTOCHEMISTRY IN WATER AND ACETONITRILE. Sophia C. Hayes, Matthew P. Philpott, Steven G. Mayer, and Philip J. Reid,* Department of Chemistry, University of Washington, Seattle, WA 98195.
The photochemistry of chlorine dioxide (OClO) in water and acetonitrile is investigated using time-resolved resonance Raman spectroscopy. Stokes and anti-Stokes spectra are measured as a function of time following photoexcitation using degenerate pump and probe wavelengths of 390 nm. The time-dependent Stokes intensities are found to be consistent with the reformation of ground-state OClO by subpicosecond geminate recombination of the primary ClO and O photofragments. This represents the first unequivocal demonstration of primary-photoproduct-geminate recombination in the condensed-phase photochemistry of OClO. Analysis of the anti-Stokes decay kinetics demonstrates that intermolecular vibrational relaxation occurs with a time-constant of ~9 ps in water and ~36 ps in acetonitrile. In addition, the appearance of symmetric-stretch anti-Stokes intensity is significantly delayed relative to geminate recombination, suggesting the excess vibrational energy is initially deposited along the asymmetric stretch co ordinate with intramolecular redistribution of this energy occurring in ~5 ps in water and ~20 ps in acetonitrile.
44. SINGLET ENERGY TRANSFER FROM CAROTENOIDS TO CYCLIC TETRAPYRROLES IN ARTIFICIAL PHOTOSYNTHETIC ANTENNAS. Alisdair N. Macpherson and Tomas Gillbro, Umea University S-901 87 Umea, Sweden, and Paul A. Liddell, Ernesto Mariño-Ochoa, Dereck Tatman, Edgardo Durantini, Devens Gust, Thomas A. Moore and Ana L. Moore*, Department of Chemistry and Biochemistry, Arizona State University, PO Box 871604, Tempe, AZ 85287-1604.
Carotenoids serve as light-harvesting pigments in photosynthesis where they absorb blue-green light and transfer energy to chlorophylls. This energy transfer process has been examined in several carotenotetrapyrrole dyads. Transient fluorescence measurements in toluene solution demonstrate that the fluorescent excited state (S2) of the carotenoid in the dyad is strongly quenched compared with the corresponding excited state in a carotenoid model compound. This quenching corresponds to ~70% efficient singlet-singlet energy transfer which matches the quantum yield obtained from steady state fluorescence measurements. The S2 state of the carotenoid is assigned the majority donor state. This observation is consistent with results from other model and natural systems.
45. PROBING INTERFACIAL WATER STRUCTURE BY VIBRATIONAL SUM FREQUENCY. Lawrence F. Scatena and Geraldine L. Richmond*, Department of Chemistry, University of Oregon, Eugene, OR 97403.
The structure and orientation of water molecules at various liquid/liquid interfaces have been probed by Vibrational Sum Frequency Generation. Specifically the region between 1975 cm-1 to 4000 cm-1 has been examined accessing the vibrational modes of H2O and D2O. Our experiments examine the interfacial equilibrium water vibrational structure of a neat interface and the changing water structure with addition of small polar molecules (i.e. CHCl3, CH2Cl2) to the CCl4 phase. We also examine the effect of small, water soluble adsorbate molecules on the structure and orientation of water molecules at and interface. The results begin to give new insight into the changing structure of the liquid/liquid interface where the subphase (CCl4) is composed of a binary mixture of polar and non-polar molecules. These studies also uncover how small adsorbate molecules affect the water vibrational structure and in turn give a molecular picture of the liquid/liquid interface.
46. SUBSTITUENT EFFECTS ON THE HYPERPORPHYRIN SPECTRA OF DIPROTONATED PARA-SUBSTITUTED MESO-TETRAPHENYLPORPHYRINS. James R. Weinkauf, Aaron S. Schweiger, Sharon W. Cooper and Carl C. Wamser*, Department of Chemistry, Portland State University, Portland, OR 97207-0751.
Porphyrins are a class of molecules which consist of four pyrrole groups in a large ring. Modifications of porphyrins include substitution at the meso-carbons by para-substituted phenyl components. In the neutral free-base form, two of the pyrrole nitrogens are hydrogen-substituted while two retain their free pair of electrons. Careful acid titrations allow for protonation of these pyrrole nitrogens and the creation of the acid dication. The acid dications exhibit red-shifted (lowered energy) absorption spectra relative to the free-base porphyrin. These red-shifts increase with the introduction of electron-donating substituents (i.e., methyl, methoxy, hydroxy, amino) of increasingly negative Hammett values. The term hyperporphyrin describes the observation of resonance delocalization of the positive dication charge from the interior pyrrole nitrogens outward to the electron-donating para substituents and the subsequent red-shifted hyperporphyrin spectrum.
47. THE USE OF INTEGRAL EQUATION AND MONTE CARLO TECHNIQUES TO UNDERSTAND THE LIGHT SCATTERING/DENSITY PROFILES OF SUPERCRITICAL FLUID BINARY MIXTURES. Frank G. Baglin*, Tasha E. Palmer, Jill E. Dougherty, Sue K. Murray and Wayne T. Stanbery, Departments of Chemistry and Chemical Engineering, University of Nevada, Reno, NV 89557 and Martin Neumann, Department of Computational Physics, University of Vienna, Vienna, Austria.
Using interaction induced Raman light scattering (iiRLS) to provide intensity/density (I/d) vs. density (d) profiles for both CH4/CO (CO2 or CF4) solute-solvent systems, Monte Carlo (MC) and Integral equation (IE) techniques have been applied to more fully comprehend the radial distribution function (rdf) properties that represent the various densities. In particular, the IE calculations have used only single center LJ molecular parameters whereas the MC use atomic centered LJ parameters and partial charges on the atoms, thus allowing the effects of dipoles and or quadrupoles to be ascertained. Moreover, the IE results have been used to calculate local density numbers which, in turn, allow us to attempt to reproduce the experimental iiRLS results.
48. A CENTRAL LIMIT THEOREM FOR CHEMICAL KINETICS IN COMPLEX SYSTEMS. Joel Z. Bandstra and Paul G. Tratnyek*, Department of Environmental Science and Engineering, Oregon Graduate Institute, Portland, OR 97291.
Reaction kinetics often appear to be first order, even in complex systems that could produce complex rate laws. This is partially due to experimental designs that emphasize initial rates and rate limiting steps, and may also be an artifact of the difficulty in resolving reaction orders from data that contain experimental noise. In addition to these familiar issues, it is also possible that complex systems are inherently more likely to be phenomenologically indistinguishable from first order. This conjecture arises by way of analogy to the central limit theorem (from statistics) wherein the distribution of a random sample, of size n, taken from any density function approaches a normal distribution as n becomes very large. To determine whether something like a "central limit theorem of chemical kinetics" applies to complex systems, we have fit first order kinetics to solutions for non-first order systems of increasing complexity. The results will be illustrated with examples from a variety of applications.
49. PANEL DISCUSSION: WHAT NEW GRADUATES NEED TO KNOW. W. Scott Briggs, Simpson Oregon Overlays, P.O. Box 17307, Portland, OR 97217.
Brief formal presentations will be given by several professional chemists who have taken a wide variety of career paths describing challenges they faced and things they wished that they had known at the start of their employment. In these remarks, the panelists will offer observations of how it "really is" in the world outside academe and what chemists-in-training can do to groom themselves for professional success and job satisfaction after graduation. Adequate time will be available for specific questions from the audience to the panelists on any pertinent concerns, and opportunity also will be available for private discussions with individual members of the panel after the formal session has closed.
50. SOLIDS ARE LIKE PEOPLE: IT'S THE DEFECTS THAT MAKE THEM INTERESTING. Arthur B. Ellis, Department of Chemistry, University of Wisconsin, Madison, WI 53706-1396.
Illustrative examples from materials science and solid-state chemistry will be presented that highlight the role of defects in determining chemical and physical properties of solids. The talk will include several demonstrations.
51. MORE ABOUT SUPERPHANES: NEW SUPERPHANES WITH FOUR- AND FIVE-MEMBERED RING SYSTEMS. Gebhard Haberhauer, Rolf Roers and Rolf Gleiter*, Organisch-Chemisches Institut der Universität Heidelberg, im Neuenheimer Feld 270, D69120 Heidelberg, Germany.
(paper copy)
52. [m.n]CYCLOPHANES AS WORKBENCHES FOR ORGANIC SYNTHESIS. Henning Hopf, Technische Universität Braunschweig, Institut für Organische Chemie, Hagenring 30, D-38106 Braunschweig, Germany.
As spacer molecules [m.n]cyclophanes are unique: they allow positioning of practically any functional group in many clearly defined geometries in three-dimensional space. As a case in point, the preparation of pseudo-geminally substituted [2.2]paracyclophanes will be discussed which are ideal workbenches for the synthesis of stereospecifically substituted cyclobutane derivatives. This topochemical control in solution can be carried out in such a way as to recover the spacer system - which hence serves as a proxy for the crystal lattice - quantitatively.
53. NEW [2.2]PARACYCLOPHANES AND MORE. Armin de Meijere*,
Oliver Reiser, Burkhard Koenig, Herwig Buchholz, Burkhard Knieriem,
and Karsten Rauch, Institut für Organische Chemie, Georg-August-Universität
Göttingen, Tammannstrasse 2, D-37077 Göttingen, Germany
[image]
Bearing on the motif of [2.2]paracyclophane 1 and its diene 2, a variety of new assemblies such as hydrocarbons 3-9 have been prepared, applying known and newly developed methodology.[1] Some of the new syntheses of such compounds, their structural, physicochemical and chemical properties will be discussed.
[image]
_______
[1] For recent reviews see: A. de Meijere, B. König, Synlett
1997, 1221-1232; B. König, Topics Curr. Chem.
1998, 196, 91-136.
54. FRONTIERS IN NON-NATURAL PORPHYRIN CHEMISTRY. Emanuel Vogel*, Martin Michels, and Lars Zander, Institut für Organische Chemie, Universität zu Köln, Greinstrasse 4, D-50939 Köln, Germany.
(paper copy)
55. CYANO- AND ETHYNYLAZULENES: VERSATILE BUILDING BLOCKS FOR NOVEL MATERIALS. Ahmed H. M. Elwahy, Kai Fabian, Stefan Schmitt, and Klaus Hafner*, Institute of Organic Chemistry, Technical University Darmstadt, D-64287 Darmstadt, Germany.
Although the chemistry of azulenes has been studied successfully for more than six decades, quite a number of conceptually simple azulenoid systems, sometimes with an extended -electron structure, remained unexplored despite their potential utility as building blocks for new functional materials, or as model compounds for an investigation of the relationship between molecular design and electronic structure. Recently we have developed new approaches for the synthesis of ethynylazulenes, which can be easily transformed into a variety of ethynyl- and butadiynyl-bridged polyazulenes. Furthermore, polycyanoazulenes proved to be a new and promising class of electron acceptors, from which CT-complexes and stable radical anions have been obtained. The syntheses, structures, and properties of the novel azulene derivatives will be discussed.
56. THE CARBON DIOXIDE TECHNOLOGY PLATFORM. Joseph M. DeSimone, Department of Chemistry, CB #3290, Venable and Kenan Laboratories, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290 and Department of Chemical Engineering, College of Engineering, North Carolina State University, Raleigh, NC 27695-7905.
What if the electronics industry used specially-designed photoresists that could be deposited using a spin coating process based upon liquid CO2 instead of organic solvents? Also what if this industry didn't have to use hundreds of millions of gallons of water per day to remove sub-micron particles during the manufacture of integrated circuits and flat panel displays? Imagine polymerizing monomers in a continuous stirred tank reactor with the resulting polymers instantly dry, avoiding the trillions of BTUs needed every year to dry commercial polymers made in aqueous reaction media. Imagine an automotive industry that doesn't expose its employees to toxic chlorinated solvents during metal degreasing processes. Imagine a textile industry that doesn't need to use 100 lbs. of water for every 1 lb. of yarn that was dyed. Imagine local dry cleaners that don't need to clean garments in perchloroethylene and local businesses that don't need to pay exorbitant, newly enacted taxes on solvent use or carry newly mandated liability insurance policies. What if the demands on municipal water systems and municipal waste water systems could be dramatically reduced by changes in manufacturing technology? Imagine an educational environment where students become grounded in the fundamentals of their core disciplines, are exposed to cutting-edge, multi-disciplinary science, and can experience the satisfaction and excitement that comes from doing research that makes a difference to society. The discussion will focus on the latest developments from the Kenan Center for the Utilization of CO2 in Manufacturing. In particular, the detailed synthesis and CO2 solution properties of fluorinated and siloxane-based homopolymers and block copolymers will be discussed. The utility of such macromolecules will also be demonstrated for use in coatings (photoresists and textiles), separations, stabilizers for polymerizations, and scaffolds for catalysis. Particular attention will focus on exploiting the compressibility of supercritical CO2 to reversibly form and break-up micelles by pressure-profiling, illustrating a critical micelle density. In addition, methods will be discussed for using supercritical extraction methods to drive step-growth polymerization reactions, both CO2-swollen melt-phase reactions as well as solid-state polymerizations, for the synthesis of polyesters, polyamides, and aromatic polycarbonates.
57. CORRELATED MANY-CHAIN DYNAMICS: ENTANGLEMENTS, SLOW MODES, AND GLASS TRANSITION. Marina Guenza, Department of Chemistry, University of Oregon, Eugene, OR 97403.
When the single polymer dynamics is hindered effectively by the presence of other chains, anomalous dynamics take place detected by the appearance of plateaus in the characteristic time correlation functions. This effect becomes dominant when the polymer molecular weight is high (entanglements) or when the system is supercooled, or when we are looking to highly dense systems. In all these cases motions can take place only through correlated mechanisms involving many chains. In this work we present a rigorous theoretical approach to describe the simultaneous correlated dynamics of several macromolecules. Starting from the Liouville equation, using Mori-Zwanzig projection operator techniques, we derived a Generalized Langevin Equation that contains, in addition to the self term, cross interaction contributions to the frequency matrix and the memory functions. The memory functions are solved using a mode-coupling approach. A self-consistent procedure allows the numerical solution of the diffusive dynamics as a function of the strength of the intermolecular potential. For weak intermolecular interactions the short-time correlated diffusive dynamics cross over to the uncorrelated single chain dynamics, while for strong intermolecular interactions collective diffusion is dominant. This effect is polymer molecular weight, polymer volume fraction, and temperature dependent.
58. EFFECTS OF SOLVENT SYSTEMS UPON THE PHASE CHANGE BEHAVIORS OF POLY(ETHYLENE GLYCOL)-CELLULOSE BLENDS. Xue-Hai Liang, Yuan-Qiang Guo and Lian-Zhen Gu, LCLC, Guangzhou Institute of Chemistry, Chinese Academy of Sciences, P. O. Box 1122, Guangzhou, China 510650.
As reported in a previous paper [1], polyethylene glycol (PEG)
blended with cellulose (CELL) was found not to melt into the liquid
state, but exhibited a crystalline-amorphous solid-solid phase
transition even as the temperature was raised to over its melting
point. Recent investigations show that the blends prepared from
solution in DMSO/PF and those in DMAC/LiCl have completely different
phase change behaviors and different miscibility. In DMAC/LiCl
the miscibility of CELL and PEG is poor, the composite obtained
exhibits a solid-liquid phase transition and has small transition
enthalpy. However, in DMSO/PF, these two polymers have a high
level of miscibility, the blend obtained exhibits a solid-solid
phase transition and has a large transition enthalpy. It is suggested
that the differences of miscibility and the phase change behaviors
are caused by the different dissolving mechanisms of CELL and
different interactions in the two solutions.
[1] X. H. Liang, Y. Q. Guo, L. Z. Gu, Macromolecules, 1995,
28, 6551-6555.
59. SYNTHESIS OF REGIOREGULAR POLY(4-SUBSTITUTED-2,2¢-BITHIOPHENE)S: POTENTIAL PRECURSORS TO ORGANIZED CONJUGATED POLYMER SOLIDS. Bennett D. Straw, Seth C. Rasmussen and James E. Hutchison*, Department of Chemistry and Materials Science Institute, University of Oregon, Eugene, OR 97403-1253.
The optical and electronic properties of conjugated organic polymers are of considerable interest for electronic applications (e.g., in polymeric conductors and field-effect transistors). The degree of order and crystallinity of the solid polymer often dictates the material performance. More highly organized solid-state structures have enhanced electrical conductivity and higher field-effect mobility. Our two-fold approach to enhancing the properties is to reduce the number of polymer side chains and control the regiochemistry of the polymer. These partially substituted, regioregular polymers should form well ordered solid state structures with a higher volume fraction of polythiophene chains than previously reported materials. Evidence for increased order in polymer solutions and solid films have been observed as bathochromic (red) shifts in the optical spectra of regioregular poly(4-substituted-2,2¢-bithiophene)s compared to regiorandom analogs. Regioregular polymers possessing carboxylic acid side chains, e.g. regioregular poly(4-carboxy-2,2¢-bithiophene), allow full characterization of the polymer and make "green" processing, in aqueous solution, possible
60. THERMOREVERSIBLE GELS FOR DELIVERY OF THERAPEUTIC AGENTS. Anna Gutowska*, Kendra A. Bennett, and Darrell R. Fisher, Pacific Northwest National Laboratory, Richland, WA 99352.
Thermosensitive hydrogels were synthesized and characterized as a novel injectable delivery system for cancer treatment. The hydrogels were synthesized with N-isopropyl acrylamide (NiPAAm) copolymerized with acrylic acid (AAc) comonomer. The copolymer gel will contain therapeutic agents such as anticancer drugs and medical radioisotopes at the injection site. Thus the copolymer will allow very high localized drug or radiation doses to tumor tissues with little effect on normal tissues. The release of 5-fluorouracil and bovine serum albumin from the NiPAAm/AAc was studied, as well as the containment of Y-90 within the copolymer. Preliminary experiments in mice and dogs show its promise as a new technology for treating solid tumors. Possible applications include treatment of prostate, pancreatic, liver, brain, and kidney cancers.
61. VAPOCHROMIC SENSORS FOR THE DETECTION OF VOLATILE ORGANIC COMPOUNDS. Leslie K. Moore*, Jay W. Grate, Marie K. Pomije, and Kent R. Mann, Center for Process Analytical Chemistry, Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195-1700.
Vapochromic materials are highly absorbing/emitting organometallic compounds that exhibit spectral shifts upon exposure to solvent vapors. In this work we studied mixed Pt-Pt salts of the general form [Pt(R-isonitrile)4][Pt(CN)4] where the functional group R is varied to enhance the selectivity of the compound to analytes of interest in industrial process and environmental monitoring. Vapochromism in these salts arises from a highly porous structure that enables the analyte molecule access to the medium sensitive chromophore. This work applies Vapochromic materials to Quartz Crystal Microbalances and Surface Acoustic Wave sensors. Simultaneous optical and acoustic measurements were performed to determine the sensitivity of the compounds to analytes such as dichloromethane, chloroform, benzene, toluene, xylene and water.
62. DYNAMIC SURFACE TENSION SENSOR FOR PROCESS MONITORING APPLICATIONS. Keith E. Miller and Robert E. Synovec,* Center for Process Analytical Chemistry, Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195-1700.
A sensor is presented that measures dynamic surface tension (DST) in aqueous, flowing systems. Surface tension is related to the surfactant concentration in solution by measuring the changing pressure across the liquid-air interface of drops repeatedly forming at the end of a capillary. A technique is presented that allows for rapid on-line calibration and DST measurement without using optical imaging equipment. This makes the sensor ideal for process control and chemical separation applications. Detection limits in the low ppm are achieved. DST measurements during early stages of drop growth (50 msecs to 1 sec) are achieved, providing insight to kinetic behavior at the liquid-air interface of surface active proteins and polymers. In addition, a novel instrumental adaptation is presented that reduces the volume of the growing drop from 7µL to the 1 to 3 µL range. Since each drop is effectively one detector "flow cell" volume, this reduction in drop volume makes the sensor well suited for microbore LC.
63. GRATING LIGHT REFLECTION SPECTROSCOPY FOR PROCESS MONITORING. Sean A. Smith, Anatol M. Brodsky, Lloyd W. Burgess*, Center for Process Analytical Chemistry, Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195-1700
Grating Light Reflection Spectroscopy (GLRS) exploits the interaction and light with a transmission diffraction grating in contact with a sample. Light reflected from this interface exhibits a redistribution of optical intensity and phase that depends on the bulk dielectric properties of the sample. Thus, one can conduct an optical transmission measurement in a reflection mode. GLRS is attractive as a process monitor because of its insensitivity to fouling layers (relative to similar techniques such as SPR or ATR), and because it can be used to characterize optically dense (~250 A.U.) and/or heterogeneous sample matrices. Past work has demonstrated the technique's usefulness in discriminating particles with diameters on the order of a few nanometers, which suggests it may also have utility as a molecular weight monitor. Currently, we are developing a micro flow-channel environment to implement GLRS as a liquid chromatography detector and to simulate the monitoring of industrial processes via a "slip-stream" arrangement.
64. LIQUID CORE WAVEGUIDES, CHARACTERIZATION AND APPLICATIONS FOR PROCESS ANALYSIS. Heather C. Edberg, Brian J. Marquardt, and Lloyd W. Burgess*, Center for Process Analytical Chemistry,. University of Washington, Box 351700, Seattle, WA 98195-1700.
Liquid core waveguides are useful in process analysis both as sampling interfaces and as whole sensing systems. These optical waveguides utilize a liquid core material of a higher refractive index than that of the cladding material. There are various cladding materials used in liquid core waveguides, many of which are Teflon-based polymers with indices of refraction from 1.29 to 1.40. With cladding refractive indices lower than that of water (1.33), it is possible to construct aqueous core waveguides. The transmission characteristics of various Teflon clad waveguides have been studied as a function of core refractive index and excitation wavelength. In this presentation we will discuss the application of aqueous core waveguides for both headspace and bulk phase analysis. We have developed specific waveguide sensors for the measurement of hydrochloric acid vapor and dissolved CO2.
65. SONOLUMINESCENCE FOR QUANTITATIVE ANALYSIS. Alex L. Robinson, Anatol M. Brodsky, Lloyd W. Burgess*, Center for Process Analytical Chemistry, Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195-1700.
Cavitation arises when ultrasonic power of sufficient intensity is applied to a liquid, disrupting the intermolecular bonds. Originating at seed nuclei, cavitation bubbles grow and collapse non-linearly during the rarefaction and compression phases of the acoustic waves, respectively. The rapid collapse of a bubble subjects the vapor contents and liquid-gas interface to temperatures and pressures on the order of 5000 Kelvin and 10,000 bar, respectively. These intense conditions last for nanoseconds in an otherwise cool liquid. Under suitable conditions, broad band, picosecond flashes of light are generated, known as multiple bubble sonoluminescence (MBSL). This light can be used for on-line, reagentless, quantitative process analysis. Certain emitting species can be identified and quantitated directly from their MBSL spectra. Information about other species may be inferred from time-intensity profiles of MBSL from the bulk solution. Controlling the physical parameters is extremely important, as bubble dynamics are also sensitive to changes in external properties such as temperature, gas content, and system acoustics. Data from alcohol, alkali and alkaline salts systems will be presented.
66. THERMAL MODULATION OF MICROCALORIMETRIC SENSORS FOR CHEMICAL ANALYSIS. M. Benton Free, Robert E. Synovec, and Lloyd W. Burgess*, Center for Process Analytical Chemistry, Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195-1700.
The thermal modulation technique utilizes thermal pulses to perturb a system slightly from equilibrium, while measuring how physical parameters of the system change over the life and subsequent decay of the pulse. The current manifestation of the technique uses off-the-shelf silicon micromachined pressure and flow sensors in a thermal pulse/thermal measurement mode, although the technique is applicable to a variety of measurement systems, e.g. thermal/optical or thermal/acoustic. Promoting a zero-order sensor to first-order using thermal modulation provides quantitative information on mixtures based on the difference in boiling points, latent heats, and sorption/desorption interactions between the analytes and the sensor surface. The chemical information is extracted from the temporal response of the sensor using multivariate analysis. Thermal modulation has been applied to deconvolute the concentrations of binary gas phase mixtures ranging from 1 to 150 ppt. It has also been used to provide near real-time, on-column monitoring of a batch distillation.
67. CHEMOMETRICS FOR BIOPHARMACEUTICAL ANALYSIS. Cliona M. Fleming* and Bruce R. Kowalski, Center for Process Analytical Chemistry, Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195-1700.
As the biotechnology industry continues to grow, there is an increasing demand for data analysis tools that will simplify the extraction of information from complex data. LC/MS is an example of an instrument that produces such data. A data processing method for LC/ESI-MS data that effectively discriminates between analyte signal and random noise has been developed. The "windowed mass selection method" (WMSM) is based on a priori knowledge of LC/MS data: as an analyte elutes, its multiply-charged ions should have a constant signal, while ions that are not part of the analyte mass spectrum should not. Unlike a boxcar moving average that will simply smooth the data, this technique actually removes random noise. This method takes advantage of the 2-dimensional structure of the data. While this method is demonstrated for biopharmaceutical data, it is also applicable to all LC/ESI-MS data, in addition to CE/MS data.
68. THE INTERMEDIACY OF STREPTOLIDINE AND CAPREOMYCIDINE IN THE BIOSYNTHESIS OF STREPTOTHRICIN F BY STREPTOMYCES L-1689-23. Michael D. Jackson1, Nuria Tamayo1, Steven J. Gould1,3, and T. Mark Zabriskie2*, 1Department of Chemistry and 2College of Pharmacy, Oregon State University, Corvallis, OR 97331, 3Merck Research Laboratories-Basic Research, Rahway, NJ 07065.
Streptothricin F (STF) is representative of the peptidyl-nucleoside family of broad-spectrum antibiotics produced by Streptomyces species. In our continuing investigation on the biosynthesis of the streptolidine portion of STF, [6-13C]streptolidine has been synthesized and introduced to production flasks containing Streptomyces L-1689-23. Isolated STF was analyzed by 13C NMR to determine the extent of incorporation of labeled streptolidine. Results showed a 1% enrichment in the resonance corresponding to the guanidino carbon of STF further supporting a convergent biosynthesis of the antibiotic. A synthesis of L-capreomycidine, a proposed precursor to streptolidine, was developed that allowed the introduction of a 13C label at the guanidino carbon. This presentation will discuss these results as well as results from [7-13C]capreomycidine incorporation studies.
69. MODIFICATION OF ARCHAEAL tRNA: CLONING, OVER-EXPRESSION AND CHARACTERIZATION OF tRNA-GUANINE TRANSGLYCOSYLASE FROM METHANOCOCCUS JANNASCHII. Ying Bai, David Fox, Judy Lacy, and Dirk Iwata-Reuyl*, Department of Chemistry, Portland State University, Portland, OR 97207.
Two structural variants of the hypermodified nucleoside 7-deazaguanosine have been identified in tRNA, queuosine, which is found at position 34 of the anticodon in bacterial and eukaryotic tRNAs, and archaeosine, which is found at position 15 of the D-loop in archae. The enzyme tRNA-guanine transglycosylase (Tgt) catalyzes a key post-transcriptional base replacement reaction in the biosynthesis of queuosine. From homology searching of the Methanoccocus jannaschii genome with E. coli Tgt, a putative archaeal tgt gene was identified and cloned. The tgt gene was over-expressed in an E. coli expression system, and the recombinant Tgt enzyme was purified. Reported here is characterization of the recombinant enzyme, including tRNA and base specificity, thermal and pH activity profiles, and steady-state kinetic analysis.
70. CHARACTERIZATION OF RECOMBINANT 1-DEOXY-D-XYLULOSE 5-PHOSPHATE ISOMEROREDUCTASE, AN ENZYME IN THE NON-MEVALONATE PATHWAY TO ISOPRENOIDS. Philip J. Proteau* , Youn-Hi Woo, and Chanokporn Phaosiri, College of Pharmacy, Oregon State University, Corvallis, OR 97331-3507.
The non-mevalonate pathway to isoprenoids is an alternate biosynthetic route to isopentenyl diphosphate (IPP) that does not involve mevalonate as an intermediate. The initial linear five-carbon precursor in the non-mevalonate pathway, 1-deoxy-D-xylulose 5-phosphate (DXP) is converted to the branched 2-C-methyl-D-erythritol 4-phosphate by DXP isomeroreductase. The enzymatic steps involved are an isomerization followed by a NADPH-mediated reduction. We have cloned the gene from the cyanobacterium Synechocystis sp. PCC6803 into E. coli and overproduced the enzyme. Efforts to purify and characterize this enzyme will be presented.
71. OLIGOSACCHARIDE SYNTHESIS BY MUTANT GLYCOSIDASES: GLYCOSYNTHASES. David L. Jakeman*, Christoph H. Mayer, Harry Brumer, Laurent Gal, J. Anthony R. Warren, and Stephen G. Withers, Department of Chemistry, University of British Columbia, Vancouver, BC, Canada V6T 161.
Glycosynthases are a new and exciting class of functional enzymes which synthesize oligosaccharides from readily accessible activated donor and acceptor sugars.[J. Am. Chem. Soc., 1998, 120, 5583] Chemical synthesis of oligosaccharides is non-trivial and, whilst transferase enzymes readily synthesize oligosaccharides in vivo, in vitro their utility is limited for two reasons, poor enzyme availability and high cost of uridine diphosphate (UDP)-sugars. The advent of Glycosynthase enzymes (developed through mechanism guided evolution) allow the use of readily prepared a-fluoride sugars as activated donors onto the oligosaccharide chain. We shall present research directed towards broadening the range of acceptor and donor sugars employed as substrates for glycosynthases and to increase the diversity and specificity of the glycosidic linkages synthesised.
72. EFFECT OF CAROTENOID BIOSYNTHESIS INHIBITION ON PRODUCTION OF TAXANES. Jon E. Reitzenstein and Angela M. Hoffman*, Department of Chemistry, University of Portland, Portland, Oregon 97203.
Paclitaxel (Taxol), a taxane diterpene from yew trees has been approved by the FDA for treatment of ovarian (1992) and breast (1994) cancer. It is an effective inhibitor of cell division by interfering with cellular microtubules. The demand for paclitaxel is on the rise as the uses for this drug are increasing. This study investigates a technique with potential for increasing the amount of paclitaxel synthesized by yew cuttings and recovered in the laboratory. Norflurazon, a carotenoid biosynthesis inhibitor, was added to liquid in which cuttings from Taxus media x hicksii were incubated. Intermediate concentrations of Norflurazon enhanced the amount of paclitaxel and other taxanes recovered from the incubation liquid. The recovery of paclitaxel from the incubation liquid is compared with its recovery from incubated plant material.
73. PACLITAXEL AND OTHER TAXANES FROM HAZELNUT CELLS AND FUNGAL ISOLATES. Angela M. Hoffman*, Harnik Gulati, Waseem Khan, Maggie Ross, and Vickashni Sundar, Departments of Chemistry and Physics, University of Portland, Portland, OR 97203.
Paclitaxel (Taxol), an anticancer drug, and several related diterpenoid taxanes were originally isolated from the Pacific yew. Recently, we have also isolated these compounds from branches of several hazelnut (Corylus) cultivars. Taxanes have been isolated from fungi associated with yew, so it was not certain whether the hazelnut tissues or a fungus associated with them were the source of the taxanes. Nineteen fungal isolates were obtained from hazelnut bark or leaves. Paclitaxel could be recovered from at least six of these fungi. We have also found paclitaxel in sterile cells cultured from hazelnut. Results from both fungal isolates and cell cultures have been verified by LC/mass spectroscopy. This is the first verified isolation of paclitaxel from angiosperm tissues. Financial support from the University of Portland and the Oregon Hazelnut Commission are gratefully acknowledged.
74. PEROXYNITRITE-MEDIATED OXIDATION OF EPINEPHRINE AND
6-NITRO-EPINEPHRINE. Bryant A. Gilbert*1, Scott
Winner1, Ranganayakulu Kurupatti1, Dagmar Bartos2, Donald D. Trunkey2,
and Matthew Slater2, 1Department of Chemistry, Portland State
University, Portland, OR 97207 and 2Department of Surgery, Oregon
Health Science University, Portland, OR 97201.
[image]
Epinephrine (1) and 6-nitroepinepherine (2) react with sodium peroxynitrite to yield adrenochrome (3) in 65 and 85% yield. The ONOOH mediated oxidation of 2 generates a very reactive 6-nitroquinone, which undergoes rapid intramolecular cyclization, followed by elimination of nitrite, to provide the oxidized product 3. The conversion of 1 and 2 to 3 via ONOOH mediated oxidation can represent a novel biological pathway for the regulation-degradation of epinephrine and its 6-nitro derivative.
75. ISOLATION OF EPINEPHRINE AND ITS OXIDATION PRODUCTS
FROM HUMAN PLASMA AND URINE. Scott Winner1, Ranganayakulu
Kurupatti1, Matthew Slater2, Dagmar Bartos2, Donald D. Trunkey2,
and Bryant A. Gilbert*1., 1Department of Chemistry, Portland State
University, Portland, OR 97207 and 2Department of Surgery, Oregon
Health Science University, Portland, OR 97201.
[image]
A two step procedure has been developed for the isolation of epinephrine (1) and its oxidation products adrenochrome (2) and adrenolutine (3) from human plasma and urine. The method involves the isolation 3 by boric acid gel trapping of 1 and 2. Acidic release of 1 and 2, followed by HPLC separation provides a fast and efficient procedure for the isolation of epinephrine and its oxidation products. Stability studies on 2 have provided time restraints for the entire procedure. In order to retain 95% of the adrenochrome in the original blood sample, the entire method must be completed within 30 minutes.
76. RADICAL CAGE EFFECTS IN THE PHOTODEGRADATION OF POLYMERS. David R. Tyler*, Dale A. Braden, Eileen E. Parrack, and Jonathan L. Male, Department of Chemistry, University of Oregon, Eugene, OR 97403-1253.
This study explored the origins of the observation that the quantum yields for polymer photodegradation depend on the polymer chain length. The (CpCH2CH2OSiR3)2Mo2(CO)6 (R = Me, i-Pr, n-Pr, n-Hx) and (CpCH2CH2NHC(O)(CH2)nCH3)2Mo2(CO)6 (n = 3, 8, 13, 18) complexes were synthesized and used as model complexes for the study. Irradiation of these molecules cleaves the metal-metal bonds and forms radicals via the intermediate formation of a radical cage pair. In the case of the silylated molecules, the quantum yields for the overall reaction with a radical trap decreased as the alkyl chain length increased. The quantum yield dependence on chain length was found to arise from changes in the cage effect. The cage effect was proportional to m1/2r2, where m is the mass of the radical and r is the radius. For the (CpCH2CH2NHC(O)(CH2)nCH3)2Mo2(CO)6 molecules, an in-cage trapping reaction occurred. This reaction is independent of chain length and therefore the quantum yields and cage effects were all identical. The effect of the solvent on the cage effect will also be discussed
77. DENSITY FUNCTIONAL THEORY CALCULATIONS ON 19-ELECTRON ORGANOMETALLIC COMPLEXES: MOLECULAR STRUCTURES AND MAGNETIC PROPERTIES. Dale A. Braden and David R. Tyler*, Department of Chemistry, University of Oregon, Eugene, OR 97403-1253.
Density functional theory (DFT) was used to calculate the molecular and electronic structures of a number of organometallic complexes that have a formal count of 19 electrons in the valence shells of the metal atom. The goals of these studies are: 1) to determine whether any structural distortions take place due to the presence of the extra electron; 2) to see if DFT can reproduce experimentally measured properties (electron-nuclear hyperfine coupling constants and Mossbauer quadrupolar coupling constants); 3) to see if the unpaired electron is localized on the metal or on a ligand; 4) when the existence of a particular 19-electron complex is uncertain, to calculate whether it is stable with respect to dissociation. We found that, in most cases, structural distortion is negligible, that DFT is capable of accurately reproducing experimental measurements, and that the unpaired electron is delocalized over the entire molecule.
78. O-ATOM TRANSFER FROM EPOXIDES TO Re(V) COMPLEXES. Kevin P. Gable, Department of Chemistry, Oregon State University, Corvallis, OR 97331-4003.
Rhenium complexes such as {(Cp*ReO)2(µ-O)2} are efficient O-atom acceptors from O2, sulfoxides and epoxides. The stoichiometric reaction of epoxides is stereospecific and high-yielding; the rate law is consistent with a mechanism involving preequilibrium scission of the dimer and rate-limiting O atom transfer from the epoxide to Cp*ReO2. Catalytic deoxygenation of epoxides using PPh3 is hampered by an unusual clustering process that siphons rhenium out of the catalytic cycle. Approaches to improved catalysis and elucidation of the mechanism of O-atom transfer are discussed.
79. SYNTHESIS AND REACTIVITY OF (Tp'ReO)2(µ-O)2. Eric C. Brown and Kevin P. Gable*, Department of Chemistry, Oregon State University, Corvallis, OR 97331-4003.
The reduction of trioxo half-sandwich Re(VII) complexes with triphenylphosphine has resulted in the formation of various oxo-bridged dimers. Although many examples of these systems have been explored, a limited amount of data is known for the dimeric rhenium(V) complex containing the hydrido-tris-(3,5-dimethylpyrazolyl)borate ligand (Tp' ligand). Recent efforts in isolating the dimeric (Tp'ReO)2(µ-O)2 (2) and its reactivity as a deoxygenation catalyst will be discussed.
80. REDUCTIVE COUPLING OF FULVENES, AN EFFICIENT METHOD FOR THE PREPARATION OF C2-SYMMETRIC ANSA-CHROMOCENE COMPLEXES. Gilbert J. Matare, Chemistry Department, University of Idaho, Moscow, ID 83844.
We have developed a high yield synthetic route to ansa-chromocenes via reductive coupling of functionalized fulvenes with activated calcium. 6,6-Dimethylfulvene, 6-phenylfulvene, 3,4-dimethoxyphenylfulvene, 6,6-diphenylfulvene, 6,6-methylphenylfulvene and 1-E-benzylidene-4,7-dimethylindene reductively couple with activated calcium to afford the corresponding ansa-calcocenes in yields of 80% or higher. We have crystallographically characterized cis and trans isomers of Ph2C2H2(h5-C5H4)2Ca(THF)2, trans-Ph2Me2C2(h5-C5H4)2Ca(THF)2 and trans-Ph2C2H2(h5-4,7-Me2C9H4)2Ca(THF)2. Transmetalation of the ansa-calcocenes with CrCl2 in the presence of Lewis bases such as CO, t-BuNC and CH3NC have been performed and will be discussed. We have recently been able to grow single crystals of ((CH3O)2Ph)2C2H2(h5-C5H4)2CrCO suitable for an X-ray analysis. Reactions of Ph2C2H2(h5-C5H4)2Ca(THF)2, with CrCl3 and CrBr3 affords the corresponding ansa-chromocene halides. The ansa-chromocene halides can be reduced to Cr(II) by magnesium powder in the presence of carbon monoxide. Work on substituting the halide ligands with other reactive hydrocarbyl ligands will also be discussed.
81. CHEMISTRY OF ELECTRON-DEFICIENT BENZOHETEROCYCLE COMPLEXES OF TRIOSMIUM CLUSTERS. Md Joynal Abedin, Edward Rosenberg*, and Kenneth I. Hardcastle, Departments of Chemistry, The University of Montana, Missoula, MT 59812 and California State University, Northridge, CA 91330.
We recently reported the synthesis and reactivity of electron
deficient triosmium complexes of quinoline where the electron
deficiency at the metal core is transmitted to the 5-position
of the quinoline ring activating it towards nucleophilic addition
reactions and thus reversing the normal reactivity of the quinoline
ring system (i.e., nucleophilic attack at the 2 or 4 position
of the heterocyclic ring).1 We have now extended this chemistry
to a broad range of heterocycles including 5,6 benzoquinoline,
phenanthridine, quinoxaline, benzothiazole, benzoxazole, benzotriazole,
and 2-substituted benzimidazoles. The synthesis and structure
of these benzheterocycle complexes will be discussed along with
the effect of ring substituents on the course of the reactions.
Preliminary results on the reactivity of these complexes with
nucleophiles, two electron donor ligands and protic acids will
also be presented.
1. E. Rosenberg, B. Bergman, K. I. Hardcastle, M. Visi, J. Ciurash,
J. Amer. Chem. Soc. 1998, 120, 12818.
82. CURRENT STATUS OF MOPAC 2000. James J. P. Stewart, Stewart Computational Chemistry, 15210 Paddington Circle, Colorado Springs, CO 80921.
The semiempirical program MOPAC has evolved steadily over the
past 15 years. While the original code was limited to calculations
of the ground state of simple gas phase molecules, the current
program is very versatile, and can model a wide range of systems.
In this presentation, a description of some of the new features
of MOPAC 2000 will be presented. These include:
* The program: dynamic memory allocation, multiprocessor capability,
range of platforms supported, program structure
* Methods: AM1-d, MNDO-d, intersystem crossing, and solvation
models
* Applications: electronic phenomena in the solid state
* Linear Scaling: enzymes and other macromolecules
* A much expanded manual to help users understand the program.
However, MOPAC should not be regarded as a finished product, rather
it should be viewed as a work in progress. Examples of features
that need to be improved are:
* According to theory, the solid state methods can be made more
efficient.
* Some optical frequency transition intensities are underestimated.
* Non-linear optics calculations need to be extended to exotic
systems.
* Some solvation models are still not sufficiently versatile.
* The accuracy of the methods in MOPAC needs to be increased.
The time scale for addressing limitations will be outlined.
83. VISUALIZATION OF CHEMICAL REACTIVITY. Sam Cole, Oxford Molecular Group, 14940 N.W. Greenbrier Parkway, Beaverton, OR 97006-5733.
Many aspects of chemical reactivity can be explored using quantum mechanical methods. We present examples that focus on the visualization of computed partial charges, frontier densities, electrostatic potentials, and frontier molecular orbitals to gain insight into chemical reactivity. MNDO methods (MOPAC) are used to calculate approximate transition-state geometries and to verify that the transition state connects to the expected reactants and products.
84. PREDICTING ATMOSPHERIC DECOMPOSITION LIFETIMES. Peter Herman, Oxford Molecular Group, 14940 NW Greenbrier Parkway, Beaverton, OR 97006-5733.
A chemical compound's environmental decomposition lifetime can be as important a property as the desirable property(s) for which it was synthesized. The ability to estimate this property prior to synthesis can save resources by screening out candidate compounds which might perform the desired function, but be too damaging to the environment. Within the last decade it has been shown that for many organic compounds the calculated HOMO energy correlates closely with the log of the molecule's rate constant for gas-phase reaction with hydroxyl radical, chief initiator of oxidation in the lower atmosphere. This offers a method to predict the atmospheric decomposition lifetime of compounds which have been designed but not yet synthesized. The well-studied example of CFC-replacement candidates will be discussed in terms both of the model's predictive usefulness, and a possible mechanistic explanation for the observed correlation.
85. CHARACTERIZATION OF ELECTROLYTES BY COMPUTER MODELING. Richard V. Whiteley, Jr., James O. Currie, Jr.*, and Kevin E. Johnson, Chemistry Department, Pacific University, Forest Grove, OR 97116.
The high voltage of the modern lithium ion battery requires an electrolyte of exceptional stability. The most successful systems use organic esters and di-esters as the electrolyte solvent. These solvents typically undergo an irreversible reduction at the lithium electrode when the battery is first charged, and this permanently diminishes the capacity of the cell. Strategies have been developed to model the reductive decomposition of the most common solvent, ethylene carbonate, and some of its more interesting analogs. The expectation is that the performance of solvents never before tested might be predicted from the model. The important issues and considerations required for a workable model are presented along with reaction pathways that are predicted by this model.
86. DFT CALCULATIONS ON Pt(CN)2(CO)2 MONOMER AND DIMER. Monia E. Hilliard, Ronald D. Poshusta,* and Glenn A. Crosby, Department of Chemistry, Washington State University, Pullman, WA 99164-4630.
Emission spectra of square planar complexes of Pt(II) are consistent with either metal-ligand charge transfer or pp* excimer models. To help resolve the uncertainty in the nature of electronic excitation in Pt(II) complexes, ab initio calculations were performed. The Pt(CN)2(CO)2 complex was chosen for the investigation as a system with enough complexity to represent typical Pt(II) complexes, and yet simple enough to be susceptible to accurate computations. A dimer of this compound was chosen as a first approximation of the structure in the crystal. A series of optimizations of both the monomer and dimer were completed employing B3LYP density functional theory and stable states were found and confirmed by vibrational frequency calculations. The stacking pattern of the molecules, the shear between the molecules and the Pt-Pt distance obtained for the dimer match fairly well those found for the halogen analog Pt(CO)2Cl2 through x-ray crystallography. Results of population analyses and DFT-based excitation calculations will also be reported.
87. MOLECULAR MODELING OF HYDROGEN ABSTRACTION AND SUBSEQUENT
RADICAL RECOMBINATION REACTIONS BY TRIPLET BENZOPHENONE. Douglas
A. Preston, Gwen P. Shusterman, and Bryant A. Gilbert*, Department
of Chemistry, Portland State University, Portland, OR 97207-0751.
[image]
Tethered benzophenones have recently garnered interest as photoaffinity labels for biological systems. Typically, the yields of these photo-labeling experiments are below 5%. High-level Density Functional Theory and ab initio calculations were performed to determine the geometry and energy associated with the hydrogen abstraction and radical recombination reactions. Application of this information towards the development of more efficient photoaffinity labels will be discussed.
88. DENSITY FUNCTIONAL THEORY AND EXPERIMENTAL EVALUATION OF OXIDATION POTENTIALS OF SUBSTITUTED CATECHOLS. John Cramer and Bryant A. Gilbert*, Department of Chemistry, Portland State University, Portland, OR 97207-0751.
[image]
High-level Density Functional Theory calculations were performed to determine the oxidation potentials of substituted catechols. The following isodesmic reaction scheme was employed to reduce systematic errors present in the calculations. A negative DG for the reaction indicates the substituted catechol would be more stable to oxidation than the parent catechol. Experimentally determined oxidation potentials of the catechols validated the theoretical method.
89. CONTROLLED FIELD EXPERIMENTS: A UNIQUE METHOD TO STUDY THE FUNDAMENTAL PROCESSES CONTROLLING THE GAS-PARTICLE PARTITIONING BEHAVIOR OF SEMIVOLATILE ORGANIC COMPOUNDS (SOCS). Brian T. Mader and James F. Pankow*, Department of Environmental Science and Engineering, Oregon Graduate Institute, Portland, OR 97291-1000.
The term semi-volatile organic compound (SOC) refers to compounds having vapor pressures between 10-11 and 10-4 atm. Many compounds of environmental interest are considered SOCs, examples are: the polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organic pesticides and aromatic organic compounds comprising secondary organic aerosols present in urban smog. Controlled field experiments (CFEs) consist of equilibrating ambient aerosols with SOCs generated in the gas phase using ambient air which has been maintained at a specific temperature and relative humidity to prevent their diurnal cycling. Such experiments reduce sampling artifacts which confound the accurate measurement of the gas-particle partition coefficients (Kps) of SOCs using conventional high-volume air sampling. Aerosol organic matter normalized gas-particle partition coefficients (Kp,om) for the partitioning of the PCDDs, PCDFs and PAHs to ambient Portland and Denver aerosols measured using CFEs will be presented. Initial data suggests it may be possible to predict the gas/particle partitioning behavior of the PCDD/Fs and PAHs at any urban location using linear free energy relationships (LFER) determined in this study, compound pure subcooled liquid vapor pressure and aerosol organic matter content.
90. DETERMINATION OF A WIDE RANGE OF VOLATILE ORGANIC COMPOUNDS IN WATER USING PURGING/ADSORPTION/THERMAL DESORPTION AND GAS CHROMATOGRAPHY/MASS SPECTROMETRY. Wentai Luo, Jay S. Hollingsworth, Lorne M. Isabelle, and James F. Pankow*, Department of Environmental Science and Engineering, Oregon Graduate Institute, Portland, OR 97291-1000.
A purge and trap method was developed for the determination of 90 volatile organic compounds (VOCs) in water. Water samples were heated and purged at 85°C and trapped with multisorbent adsorption/thermal desorption (ATD) air sampling cartridges. The ATD cartridges were thermally desorbed and analyzed by GC/MS. The VOCs are halogenated alkanes, halogenated alkenes, ethers, alcohols, nitriles, esters, ketones, aromatics, a disulfide, and a furan. This group includes compounds such as tert-butyl alcohol and tert-amyl alcohol can not be measured by currently available purge and trap methods at low levels. The volatility of the target VOCs from water range from that of dichlorofluoromethane (CHFCl2) down to that of alcohols. The method detection limit (MDL) values range from 0.01 ppb (mg/L) to 0.5 ppb for a 5 mL sample.
91. ASSESSING THE ENVIRONMENTAL FATE OF METHYL TERT-BUTYL ETHER. Clinton D. Church, James F. Pankow and Paul G. Tratnyek*, Department of Environmental Science and Technology, Oregon Graduate Institute of Science and Technology, Portland, OR 97291-1000.
The concern over contamination of groundwater by methyl tert-butyl ether (MTBE) has increased the need for a better understanding of the processes that control its environmental fate. As part of a study to characterize the kinetics and mechanisms of MTBE degradation, we developed a direct aqueous injection (DAI) GC/MS technique that allows us to simultaneously analyze for MTBE and its expected degradation products at the sub-ppb level. We used the method to explore the abiotic hydrolysis of tert-butyl formate (TBF, a major product of MTBE photooxidation) to tert-butyl alcohol (TBA). We found that TBF is subject to rapid neutral and acid/base catalyzed hydrolysis with half-lives at 22°C of approximately 5 days, 8 hours, and 8 minutes, respectively. When the method was applied to effluent from aerobically fed column microcosms prepared with aseptic core materials from three pristine sites, conversion of MTBE to TBA was observed after a lag period of approximately 35 days, but no evidence of TBA degradation was observed. In similar columns with anaerobic feeds or with BTEX (gasoline constituents- benzene, toluene, ethyl-benzene, and o-, m-, and p-xylenes) contaminated aerobic feeds, however, we have not seen any evidence of MTBE degradation up to 120 days. We have also used the method to analyze groundwater samples from a number of sites, representing a wide range of aquifer conditions. To date, these samples have not produced unequivocal evidence of MTBE degradation. The combined results presented here suggest that microbial degradation of MTBE may occur to a limited extent under aerobic conditions. This degradation is unlikely to be a rapid or widespread process in the subsurface environment, however, even though appreciable conversion is readily achieved under controlled conditions in the laboratory.
92. EVALUATING THE EFFECT OF IN-SITU AIR SPARGING ON AQUEOUS MTBE CONCENTRATIONS. Illa L. Amerson-Treat* and Richard. L. Johnson, Department of Environmental Science and Engineering, Oregon Graduate Institute, Portland, OR 97291-1000.
In-situ air sparging (IAS) is a remediation technology commonly used for gasoline contamination. The premise is that the injected air will remove volatile organic compounds (VOCs) by volatilization and enhance aerobic biodegradation processes. In general, IAS effectiveness is limited to zones where the contaminant and injected air are in close contact. Because of this, some rebounding of contaminant concentrations is typically seen following system shutdown. This rebounding may pose a significant problem with respect to MTBE. Gasoline may contain >10% MTBE by volume. Due to its high solubility, MTBE remaining in any residual non-aqueous phase gasoline not removed by IAS will dissolve quickly and may result in elevated aqueous concentrations once again. A large 3-dimensional physical model is being used to simulate the conditions of a gasoline spill and resulting contaminant plume. The physical model allows extensive plume characterization and monitoring which is not typically feasible at gasoline release sites. This paper will present the results of the quasi-field scale experiment and discuss whether or not IAS has the potential to permanently reduce aqueous MTBE concentrations.
93. HYDROLYTIC TRANSFORMATION OF TKEBS BY SUBSURFACE SOLIDS FROM A CONTAMINATED SITE. M. Chu and L. Semprini*, Department of Civil, Construction, and Environmental Engineering, Oregon State University, Corvallis, OR 97330.
Tetrakis(2-ethylbutanoxy)silane (TKEBS) is present along with trichloroethene (TCE) as a subsurface contaminants at Site 300, Lawrence Livermore National Laboratory (LLNL), CA. The anaerobic transformation of TCE is driven by the fermentation of a hydrolytic product of TKEBS, 2-ethylbutanol. Therefore, the understanding of the hydrolytic degradation of TKEBS under site conditions will help in the understanding of transformation processes occurring at the site. This study investigated the abiotic hydrolytic transformation of TKEBS at different initial water contents and different particle sizes with soil from the site. The rates and products of TKEBS transformation in batch kinetic tests were determined by dichloromethane extraction and gas chromatography. The results showed that all particle sizes had catalytic ability to accelerate the hydrolysis of TKEBS. However, smaller particles consisting of silt and clay did not show greater ability to enhance TKEBS transformation. Studies are currently being performed to evaluate the effect of soil water content on TKEBS transformation
94. PILOT SCALE DEMONSTRATION OF A SURFACTANT MODIFIED ZEOLITE PERMEABLE BARRIER. Timothy L. Johnson* and Richard L. Johnson, Oregon Graduate Institute, Portland, OR 97291.
Permeable barriers are gaining acceptance as a means to remediate shallow groundwater contamination plumes. Mixed waste plumes, consisting of organic and inorganic contaminants, are especially difficult to remediate due to the varying chemical properties of the constituents. Surfactant-modified zeolite has been shown to sorb and retard inorganic oxyanions, heavy metal cations, and a broad range of organic contaminants. Zeolites are naturally occurring aluminosilicates with open, cage-like structures and high internal and external exchange capacities. Surfactant modification of zeolite constitutes replacing base cations on the external exchange sites of unaltered zeolite with a cationic surfactant. A pilot-scale demonstration was conducted at the OGI Large Experimental Aquifer Program to test the use of surfactant modified zeolite as a permeable barrier material for remediation of PCE and Cr. The LEAP site at OGI is designed to facilitate large-scale transport experiments by offering controllable aquifer flow regimes, a high-density sample acquisition network, and onsite data analysis, while maintaining a safe and containable contaminant delivery system.
95. HIGH EFFICIENCY ENVIRONMENTAL SORBENT MATERIALS: SELF-ASSEMBLED MONOLAYERS ON MESOPOROUS SUPPORTS (SAMMS) FOR METAL REMOVAL FROM AQUEOUS SYSTEMS. Glen E. Fryxell*, Jun Liu, Teresa A. Hauser, Zimin Nie, Richard T. Hallen, Mauxu Qian, and Kim F. Ferris, Pacific Northwest National Laboratories, Richland, WA 99352.
Mesoporous silica (MCM-41) was effectively functionalized with a self-assembled monolayer composed of ethylenediamine terminated silanes. The details of the optimized derivatization will be presented. These aminated mesoporous supports were then tested for their binding affinities with a variety of transition metal cations of environmental concern (Cu, Co, Ni, Cd, Pb, etc.). Details on loading capacity, distribution coefficients, and characterization will be summarized.
96. GROUND WATER STUDIES IN TOPPENISH WASHINGTON. Hossein R. Divanfard*, Herman Moya, and Ron Sell, Heritage College, Toppenish, WA 98934.
In 1998 a project conducted at Heritage College monitored the concentration of combined nitrate-nitrite and the pesticides atrazine and diazinon in drinking water wells in the Toppenish Basin. Water samples were collected and analyzed on a weekly basis. The results showed that the combined nitrate and nitrite concentrations remained relatively constant throughout the irrigation period at all of the sites. At the two wells in the vicinity of Harrah, WA, however, the combined nitrate and nitrite exceeded regulator standards brought forth in the Safe Drinking Water Act of 1972. Based on previous work by the USGS in 1979 and 1989, the concentration of combined nitrite and nitrates has increased 176%, in one case, over a period of 19 years. The pesticides were not detected in any of the wells. This project was student oriented. Eight undergraduate students were involved in QA-QC development, training, site selection, sampling, analysis and report writing.
97. DETECTING THE GEOGRAPHIC ORIGIN OF FOODS. Kim A. Anderson1* and Brian W. Smith2, 1Department of Food Science and Toxicology, Analytical Sciences Laboratory, Holm Research Center, University of Idaho, Moscow, ID 83844-2201. 2Department of Pure and Applied Mathematics, Washington State University, Pullman, WA 99164.
The determination of geographic origin of raw commodities and food products through chemical analysis is timely. Economic incentives continue to drive some retailers to mis-identify geographic origin of raw commodities and food products. The determination of geographic origin is important for both enforcement options for the food industry and protection of the consumer from overpayment and deception. Mis-identifying geographic origin of raw commodities and food products is a concern for growers and consumers and includes issues of quality, safety and consumer's preferences. Using trace element analysis including Ba, Cd, Cr, Co, Cu, Fe, Mo, Mn, Ni, V, Zn, K, Mg, P, Pb, and Sr coupled with sophisticated data analysis; geographic origin of foods can be determined. Results for several foods will be presented, including apples and coffee. Demonstration of capability for determining geographic origin of apples from two growing regions will be presented. Apples from Washington (W) and New Zealand (Z) are compared using Canonical Discriminant Analysis (CDA). Trace element data for roasted coffees from eight different growing regions, including South/Central America, Africa and Indonesia will also be presented.
98. DEMONSTRATION OF MAGNETIC PROPERTIES OF FE, FERRIC ION, PERMANGANATE ION, AND MANGANESE DIOXIDE. David Ehrenkranz, Westview High School, 4200 NW 185th Ave., Portland, OR 97229.
Using two neodymium-boron-iron magnets, the magnetic properties of Fe, ferric ion, permanganate ion, and manganese dioxide will be demonstrated and correlated with their electronic structures and spin.
99. INTERMOLECULAR FORCES. Marcy Martone, Century High School, 2002 SW 234th Ave., Hillsboro, OR 97214.
Grade Level: Chemistry or Integrated Science.
Technology: CBL, Graphing Calculator (CHEMBIO program), temperature
probes
Materials: isopropyl alcohol and distilled water
Why do we perspire? A chemical demonstration showing the rate
of evaporation of water and isopropyl alcohol. Students will look
at cooling curves to begin discussion of hydrogen bonding and
dipoles. Additional demo will be provided if technology is not
available to teachers.
100. ALTERING REACTION RATES. Arnie Ariss, Hillsboro High School, 3285 SE Rood Bridge Road, Hillsboro, OR 97213.
A demonstration to show one of the factors affecting the rate of reaction, using equipment that you may already have in your stockroom. Simple homemade equipment will shown that will easily accomplished the desired reaction. Then using the apparatus (paint can w/ attachments), a watch glass, flame source(candle), and powdered starch, the rate demonstration will be conducted.
101. THE ORANGE CLOCK REDOX DEMONSTRATION: WHO IS ACCEPTING ELECTRONS AT THE CATHODE? Katy Olsen and Todd P. Silverstein*, Chemistry Department, Willamette University, Salem, OR 97301.
A common electrochemistry demonstration produces electrical current from fruit juices and other foods and beverages. Typically, strips of copper and zinc (or magnesium) are placed in a fruit or beverage and connected to the battery terminals of a clock. The voltage and current produced by oxidation of the zinc (or magnesium) are sufficient to run the clock for several days. There has been however some debate as to the nature of the cathode half reaction: Some suggest that either hydrogen ions or water are reduced at the cathode. If this is true, voltage should decrease by about 60 mV per pH unit, according to the Nernst equation. In this project we measured the voltage across copper/magnesium and copper/zinc strips in different solutions and beverages, buffered at various pH's. Under certain conditions we did observe the expected -60mV/pH unit slope, but under other conditions the deviation from Nernst theory was substantial. Deeper exploration of a seemingly simple electrochemistry class demonstration has led us to some surprising conclusions.
102. CATALYTIC DECOMPOSITION OF ACETONE. Dennis B. McKinney, Orcas Island High School, Eastsound, WA 98245.
This is an easy, safe way to demonstrate the function of a catalyst to your high school chemistry students. A heated copper penny is suspended above a container of acetone. When the heated penny is surrounded by a mixture of air (O2) and acetone vapor, catalysis occurs at the surface of the copper converting the mixture to water and carbon dioxide. This reaction is sufficiently exothermic to keep the penny hot and the process self sustaining.
103. STUDENT OBSERVATION OF SCIENCE "MYSTERY" CHEMICAL REACTION CALLED OLD FOAMY, ALSO CALLED ELEPHANT'S TOOTHPASTE. Lynn L. Mitchell, Chemistry Teacher, Hood River Valley High School, 2763 Montello, Hood River, OR 97031.
To enhance my classes I perform various experiments and have my students write about what they observe. This experiment involves placing 5.0 mL of dish soap in a 500 mL graduated cylinder along with 10.0 mL of 30 % sodium peroxide. Then add 10.0 mL of a 1.0 M solution of potassium iodide, stand back and let the reaction take place. Additional "mysteries" may be demonstrated if time permits. The idea for "Old Foamy" reaction came from Flynn Fax, distributed by Flynn Scientific Company.
104. THE LIQUID NITROGEN FOUNTAIN. Jeffrey A. Rahn*, Robin P. McRae, Timothy M. Beamer, and Norm LeBret, Department of Chemistry, Eastern Washington University, Cheney, WA 99004-2431.
Details of a demonstration using liquid nitrogen are presented. The demonstration is based on a 500-mL transparent polyethylene soft drink bottle with a screw-on pop-up drink top. Prior to the demonstration, a balloon is placed over the popped-up spout of the bottle top. The drink bottle is filled with liquid nitrogen and the top, with the balloon affixed, is quickly put in place and screwed on tight. As the liquid nitrogen in the bottle boils, the balloon inflates. When the balloon bursts the noise produced is far greater than would ordinarily be expected, and a fountain of liquid nitrogen and condensing water vapor shoots into the air above the bottle.
105. SOME FAVORITE DEMONSTRATIONS. Tom Dunne*, Chemistry Department, Reed College, Portland, OR 97202-8199.
A few simple, favorite demonstrations will be attempted. Related principles of chemistry will be indicated.
106. GRADUATE SCHOOL PREPARATION: SEMINAR AND PANEL DISCUSSION. Morton Z. Hoffman, Department of Chemistry, Boston University, Boston, MA 02215.
This seminar and discussion will cover everything you ever
wanted to know about graduate school in the chemical sciences:
how to get in, how to stay in, and how to get out (in a reasonable
length of time). A
panel of graduate students will also discuss life in graduate
school.
107. HIGHLY SELECTIVE STATIONARY PHASES FOR CAPILLARY HPLC AND CEC BASED ON MOLECULAR IMPRINTED POLYMERS. Patrick T. Vallano, Gabriela Chirica and Vincent T. Remcho*, Department of Chemistry, Oregon State University, Corvallis, OR 97331.
Molecular imprinting is a technique in which specific recognition sites are formed in a polymer matrix by synthesizing the polymer in the presence of a template molecule. The resultant imprinted polymer, or MIP, is capable of selectively rebinding the template, even in the presence of structurally similar species. The high selectivity of the recognition process has rendered MIPs useful in several areas of analytical chemistry including sensors, immunoassays and separations. The focus of this work is the use of molecular imprinted polymers as highly selective stationary phases in capillary HPLC and CEC. The imprinted polymers employed in this study were synthesized in bulk, ground and sieved to yield particles with a nominal diameter of less than 30 mm. The MIP particles were then packed into fused silica capillaries using a slurry method. Baseline resolution of the template from a series of closely related structural analogs was obtained with MIPs prepared with nortriptyline, a tricyclic antidepressant drug, as the imprinted species. A separation of the same mixture was not possible on a reference capillary (i.e., polymer prepared under identical conditions in the absence of template).
108. HPLC COLUMN SWITCH METHOD TO QUANTITATE ENANTIOMERS IN HUMAN PLASMA. Jin Y. Huang, Daniel H. Marchand and John W. Dolan*, LC Resources Inc., 3138 NE Rivergate Bldg. 301C, McMinnville, OR 97128.
A HPLC column switching method to quantitate enantiomers in human plasma was developed. The method was intended to support studies determining if metabolic racemization is occurring. The sample preparation procedure consisted of manual solid phase extraction. The samples were analyzed by chiral HPLC with a column-switching method. This involved injecting the samples onto the primary column and then diverting the enantiomers onto the chiral column. This diversion occurred just prior to the elution of the enantiomers. The system was then returned to its original configuration, which allowed for the re-equilibration of the primary column. The system configuration was next changed to allow for detection of enantiomers as they eluted from the chiral column. Detection was by fluorescence. The ruggedness of the method was tested over a three-day period. The sensitivity limit of the assay was determined to be 0.003 mg/ml of enantiomer in human plasma.
109. GRADIENT HPLC BACKGROUND PEAKS - A CASE STUDY. Michael D. Nelson and John. W. Dolan*, LC Resources Inc., 3138 NE Rivergate, Bldg. 301C, McMinnville, OR 97128.
A problem that occurs in high performance liquid chromatography (HPLC) runs is the presence of spurious peaks in blank baselines during gradient runs. These peaks occur when no sample is injected, indicating the peaks must originate from the mobile phase buffers or from other system components. Peaks of about 0.05% of the area of the parent peak are of concern in pharmaceutical degradation studies. Such baseline peaks make difficult the task of determining which peaks are actually sample related, and which are due to the system. It was necessary to determine the source of these peaks and to try to eliminate them. It was suspected that the buffer manufacturer was not supplying clean phosphate. When several different brands were compared, peak profiles were similar, indicating that the peaks originated from the system, and not the buffer. There were several steps in the buffer preparation process that were suspected of causing contamination. These were glassware contact, microfiltration, pH adjustment, and degassing. Each of these was isolated and examined. Contact with glassware and pH adjustment were found to cause the majority of the contamination. Rinsing all glassware prior to use and external pH reading was sufficient to greatly improve spurious baseline peaks.
110. FRITLESS CAPILLARY COLUMNS BASED ON CONVENTIONAL HPLC PACKING MATERIALS. Gabriela S. Chirica, Patrick T. Vallano, and Vincent T. Remcho*, Department. of Chemistry, Oregon State University, Corvallis, OR 97331-4003.
A principal driving force in the continued development of Capillary Electrokinetic Chromatography is to enhance its suitability for routine analytical work. This study addresses the issue of column fragility, proposing "entrapped" columns as an alternative to routine frit-retained packed beds. A solution of monomers is introduced into a capillary packed with a conventional HPLC sorbent and allowed to polymerize yielding a medium in which the packing material is stabilized and retained inside the capillary by the polymer matrix. Columns prepared using this technique are mechanically robust and can be cut to any desired length. These entrapped columns are suitable for both micro HPLC as well as CEC. The chromatographic performance of the initial packing material remains largely unaffected by the treatment. The entrapment matrix can be designed so as to introduce ionizable groups. This extends the range of materials that may be used as sorbents for CEC separations.
111. TEMPERATURE CONTROL IN HPLC. Robert G. Wolcott1 and John W. Dolan2*, 1Linfield College, Department of Chemistry, McMinnville, OR 97128 and 2LC Resources Inc., 3138 NE Rivergate, Bldg. 301C, McMinnville, OR 97128.
Control of temperature in high performance liquid chromatography (HPLC) operation is critical for achieving reliable, repeatable results. Two major problems must be overcome: (a) column temperature must be kept constant, and (b) temperature of incoming solvent must be constant and equal to that of the column. Consequences of poor temperature control include changes in retention time of 1-2% per °C, changes in separation selectivity for certain pairs of compounds, and reduction of column plate height. Problems in setting and stabilizing column and incoming solvent temperatures include variations related to location within an oven, temperature controller accuracy and sensitivity, and cost and performance of monitoring equipment. This poster compares use of active and passive preheating of incoming solvent, block heater and forced air ovens, and describes a "chemical thermometer" that can be used to estimate average column temperature independent of monitoring equipment and flow rate. Simple suggestions are offered for achieving a close match between temperatures of incoming solvent and column, and optimizing thermal factors that affect HPLC system performance.
112. BASELINE DEVIATIONS IN RP-HPLC WITH TRIFLUOROACETIC ACID - ACETONITRILE GRADIENTS. Nan S. Wilson and John W. Dolan*, LC Resources Inc., 3138 NE Rivergate, Bldg. 301C, McMinnville, OR 97128.
Trifluoroacetic acid-water-acetonitrile (TFA-ACN) reversed-phase high performance liquid chromatography (RP-HPLC) gradient methods are widely used for analysis of pharmaceutical and biological compounds. Blank baselines monitored at 225 nm show unusual negative dips as the gradient reaches 100% ACN. Nonlinearity of TFA-ACN baselines have been reported earlier, however, the observed post-gradient baseline dips were unexpected. This phenomenon is attributed to the nonlinear uptake of TFA by the stationary phase as the ionization of TFA abruptly changes near 100% ACN. The behavior is more pronounced with longer columns and/or less polar stationary phases. This problem is of minimal importance if gradients of >90% ACN/TFA are avoided when detection at 225 ±5 nm is used.
(Note - the poster previously listed as # 113 is now # 107)
113. CHARACTERIZATION OF SULFATED ZIRCONIA. Susmita
Bose,* Yun You,** Anand Chellappa,** William Thomson,** and
Yang Wang,*** *School of Mechanical and Materials Engineering,
**Department of Chemical Engineering, Washington State University,
Pullman, WA 99164 and Battelle Pacific Northwest National Laboratory,
Richland, WA 99352.
Bulk catalysts consisting of sulfated zirconia (SZ), and iron and manganese promoted sulfated zirconia, as well as sulfated zirconia supported on mesopore silica, were prepared and investigated by different characterization techniques. Solid supported acid catalysts can replace concentrated acids to perform various acid catalyzed organic reactions. The surface acidic properties of various solid supported acid catalysts were evaluated by measuring adsorbed ammonia using temperature programmed desorption (TPD) method. Quantitative measurements of Lewis and Bronsted acidity on solid acid catalysts, in-situ, was measured using IR spectroscopic method. These measurements were then correlated for each catalyst with their catalytic activity for n-butane isomerization. The presentation will include various catalytic activity measurements of different catalysts with respect to their acidity.
114. DATABASE CHANGE CONTROL FOR TANK WASTE INFORMATION NETWORK SYSTEM INTERFACE. Rebecca A Bechtold,* Melvin R. Adams, and Kathleen M. Hall, Pacific Northwest National Laboratory, Richland, WA 99352.
The Tank Waste Information Network System [TWINS] is a publicly accessible web-based interface system for tank waste characterization information at the Hanford site. The TWINS provides a single convenient point-of-access for obtaining a growing quantity of tank data for Hanford's 177 Underground Storage tanks and miscellaneous tanks. The Hanford Tank Characterization Database currently contains in excess of 800K records, and management of the information requires constant attention to assure that the quality of information is of the highest caliber. This paper describes the current methodology for tracking and correcting data deficiencies through the change process. In addition, the computer has been programmed to identify certain common types of data deficiencies. As data problems are investigated and corrected, an independent software system is used for documenting and tracking the issue throughout its resolution.
115. DETERMINATION OF TRACE LEVELS OF Fe(II) AND TOTAL Fe IN NONREFRACTORY MINERALS USING 1,10-PHENANTHROLINE. Bryan K. Reichert1, Amy L. Fong1, J. Charles Templeton1, James E. Amonette2, 1Department of Chemistry, Whitman College, Walla Walla, WA 99362; 2Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352.
When our 1,10-phenanthroline method was used to quantify trace levels of Fe(II) and total Fe in nonrefractory minerals, errors associated with equilibration time, Fe content, and sample weighing were identified. For both Fe(II) and total-Fe measurements, equilibration times of 2 h after addition of color-promoting reagents (i.e., 1% citrate or 1% citrate/1% NH2OH) were needed to reach maximum absorbance. This period contrasts with immediate color development for Fe(II) determinations and a 90-minute period for total Fe when routine samples are analyzed. Greater uncertainty in sample weights was also observed when small sample sizes (<30 mg) of the primary standard [ferrous ethylenediammonium sulfate (FES)] were analyzed. This problem was resolved by diluting FES powder 10-fold in reagent-grade Na2SO4 to create a new standard for trace-level Fe analyses. With these procedural changes, analysis of trace levels of Fe can be achieved with the same accuracy and precision expected for routine samples.
116. STEREOCHEMICAL STUDIES OF 1-DEOXY-D-XYLULOSE-5-PHOSPHATE ISOMEROREDUCTASE, AN ENZYME IN THE NONMEVALONATE PATHWAY TO ISOPRENOIDS. Youn-Hi Woo, Chanokporn Phaosiri, and Philip J. Proteau*, College of Pharmacy, Oregon State University, Corvallis, OR 97331-3507.
The non-mevalonate pathway is an alternate biosynthetic route in some bacteria, algae and plants to isopentenyl diphosphate (IPP), which is the building block of isoprenoid metabolites. This recently described pathway proceeds via 1-deoxy-D-xylulose-5-phosphate (DXP), which is converted to 2-C-methyl-D-erythritol-4-phosphate by DXP isomeroreductase. The stereochemistry of the reduction step of this enzymatic conversion was investigated. The isomeroreductase gene (dxr) from the cyanobacterium, Synechocystis sp., was overexpressed in E. coli. The two necessary substrates to examine the stereochemistry, DXP and (3S)-1-deoxy-[3-2H]-D-xylulose-5-phosphate, were both chemically synthesized from propargyl alcohol in 9 steps with 11% overall yield. The unlabeled DXP will be incubated with the isomeroreductase in the presence of deuterated NADPH (NADPD) while the 3-2H-DXP will be treated with NADPH. The two monodeuterated 2-C-methyl-D-erythritol-4-phosphate products will be converted to the bisacetonides of 2-C-methylerythritol and analyzed using a combination of NOE and 2H NMR experiments.
117. MECHANISTIC STUDIES OF QueA, AN ENZYME INVOLVED IN THE HYPERMODIFICATION OF tRNA. Sylvia Daoud Kinzie, Bernd Thern, and Dirk Iwata-Reuyl*, Department of Chemistry, Portland State University, Portland, OR 97207.
Queuosine (Q) is a hypermodified base present in specific tRNAs (Asn, Asp, Tyr and His) and occurs as a post-transcriptional modification of the wobble base G34. Although it is found in both eubacteria and eucaryotes, its de novo biosynthesis is a unique property of eubacteria. We are investigating the biochemical pathway responsible for queuosine biosynthesis, with particular emphasis on the enzyme S-adenosylmethionine: tRNA ribosyltransferase-isomerase (QueA). QueA catalyzes the conversion of the ribosyl moiety of S-adenosyl-L-methionine (AdoMet) to the epoxycyclopentandiol residue of epoxyqueuosine (oQ), the penultimate intermediate in Q-biosynthesis. We have proposed a new chemical mechanism for this unprecedented reaction, and present experiments designed to test this proposal.
(Note - poster previously listed as # 118 has been withdrawn)
118. APPLICATION OF DHBA TO BLEACH HARDWOOD KRAFT PULP.
Eileen O. Kutscha*, Barry S. Goodell**, Douglas M. Ruthven,
and Joseph M. Genco, Department of Chemical Engineering and **Department
of Wood Science and Technology, University of Maine, Orono, ME
04469.
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