Summer Research
Faculty Research Interests
Jonathan A. Bohmann, Associate Professor
Dr. Bohmann’s research into dissection of NMR chemical shifts in terms of contributions from localized and delocalized molecular orbitals continues. The projects are based on the calculation of NMR chemical shifts from
ab initio and DFT molecular orbital theory. He employs the Natural Chemical Shielding (NCS) analysis computer program, which carries out the dissection of NMR shifts. NCS is available as part of the Natural Bond Orbital (NBO) program. Recently, the
GAUSSIAN 03 theoretical chemistry program was released with a version of his NCS analysis.
Collaborations with Zhongfang Chen and the theoretical chemistry group of Paul V.R. Schleyer at the University of Georgia continue. He has begun new collaborations with a group in Italy and continues to work in close collaboration with the Theoretical Chemistry Institute at the University of Wisconsin-Madison.
One of the student research projects is a look into the proposed “ring-current” effect of NMR shielding in carbon cage compounds. The NCS method provides a way to look at the magnetic shielding due to each bond (electron pair localized orbital) in such molecules, using the latest GIAO (gauge-including atomic orbital) method with DFT calculations. Such bond contributions may provide a way to detect a small ring current, if it exists.
A new direction of research for this group is ion fragmentation chemistry, as studied from the perspective of high-accuracy ab-initio methods including G2, G3 and CBS techniques. Last November two senior chemistry majors, Amanda Schuckman and Crystal Wiedner, traveled to the Joint Southwest / Southeast Regional ACS meeting to present their work on the unusual ion fragmentation of phenylisocyanate.
Back to top John V. McClusky, Associate Professor
Electrophilic addition to conjugated dienyl ethers often passes through the
much less stable carbocation intermediate. Our work to synthesize related analogues to the ethers has been challenging. Elimination of 1,2,3-tribromocyclohexane to form isomeric bromocyclohexadienes has been successfully completed with LDA; work is now in progress to purify the product and examine its addition chemistry. The synthesis of 1,3-cyclohexadienyl ethyl sulfide is progressing. 2-cyclohexenyl ethyl sulfide has been synthesized in high yield and purity; however, elimination of 2,3-dibromocyclohexyl ethyl sulfide and 1- and 3-bromocyclohexenyl ethyl sulfide are quite sluggish. We are continuing our work to solve these problems.
Nanocomposite polymers have received a great deal of interest in the past several years due to their exceptionally high toughness and strength, especially for polyolefin and nylon polymers. Attempts to develop nanocomposite polyurethanes, however, have met with mixed success. We have synthesized a variety of hydroxy-functionalized ammonium clays and incorporated them into polyurethane polymers. The polymers contained polyols with high and low hydrophobicity, and varying amounts of butanediol chain extender. In all cases these new organoclays roughly doubled the percent elongation and tensile strength of the polymers with minimal effect on the Young’s modulus. We were very surprised to discover that the presence of hard segment is critical for increased properties: polymers with the organoclays yet without the typical chain extender had properties and very close to the control samples. Finally, these organoclays improve the physical properties in polyurethanes both with and without hard domains.
Back to top David Wasmund, Professor
The main focus of research in our laboratory continues to be the chemistry of titanium complexes with the metal in an oxidation state of +2 or +3. We have synthesized a series of octahedral Ti(II) halide (Cl-, Br-, I-) complexes of pyridine and 4-picoline. These complexes were synthesized by the reduction of Ti(III) or (IV) halides with lithium with the ligand acting as the solvent. Results of these studies have been reported at various ACS meetings. We have demonstrated that 2-picoline and 3-picoline do not form complexes with Ti(II), the amine being preferentially reduced. We are currently investigating complexes of Ti(II) with other ligands, such as crown ethers and phosphorus ligands. All these complexes are exceedingly air sensitive and vacuum line and other air-sensitive techniques must be used. Students also learn glassblowing.
We also are investigating the reaction of the pyridine and the picolines with alkali metals. It is known that anhydrous pyridine reacts with alkali metals to form predominately the 4,4’-dipyridyl radical anion. We are investigating the mechanism of this reaction. The reaction of 4-picoline with an alkali metal would be expected to form the 4,4’-dimethyl-2,2’-dipyridyl radical anion. The visible spectra of this anion and of the 5,5’-dimethyl isomer were obtained and compared with the spectra of the product of the reaction between 4-picoline and sodium. The spectra of 2-picoline plus sodium and 3-picoline plus sodium were also measured. We compared our spectra versus that predicted by several theoretical methods, including ZINDO and
ab initio methods on a parallel processing computer cluster. Dr Bohmann is collaborating with this research. It was also reported at the ACS meeting in San Antonio.
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Chemistry Summer Research Gallery
Our Summer Research Students
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Inorganic Synthesis
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Computational Chemistry
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Organic Reactions Catalyzed by Clay
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Glassblowing with Dr. Wasmund
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Using HPLC Instrumentation
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Polymer Chemistry Research
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Lab work
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One afternoon out of the lab for tubing!
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Floating down the San Marcos River
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