Summer Research 2013

Summer research 2013

Celebration of Summer Research September 5, 2013

Abstracts of chemistry student poster presentations

 

Effects of n-Propanol on Excimers of 2-Methylnaphthalene on α-Alumina

The thin film interactions of n-Propanol (n-PrOH) and 2-Methylnaphthalene (2-MN) during excimer formation were observed on α-alumina by monitoring laser-induced fluorescence (LIF) decay rate constants, intercepts, and wavelength-resolved spectra during temperature programmed desorption (TPD). :
Brandon D. Driver ‘14, Marcus B. Anthony (Point Loma)’14, Nicole K. Grabe ‘13, A.M. Nishimura,Professor Emeritus of Chemistry, K.A. Martin

Effects of Simple Aliphatic Alcohols on Naphthalene Excimers on α-Alumina

Temperature programmed desorption (TPD) experiments were run on bilayers of various simple aliphatic alcohols and naphthalene, both of which were amorphously deposited in a high vacuum chamber on the surface of an α-alumina crystal. The excimer fluorescence of napthalene was induced by either a pulse laser or a mercury lamp. Laser induced fluorescence (LIF) decay rate constants show the presence of an alcohol causes a minimum in the rate constant to occur during the temperature range of the alcohol’s desorption. Annealing the alcohol-naphthalene bilayer showed an irreversible character resulting from lower energy excimer conformations forming; the naphthalene multilayer was reversible as a result of its inability to rearrange into a lower energy excimer. The methanol-naphthalene bilayer was representative of this effect. 
Nicole K. Grabe ‘13*, Marcus B. Anthony’14*‡, Brandon D. Driver ‘14*, K.A. Martin‡ and A.M. Nishimura, Professor Emeritus of Chemistry, Westmont College, Santa Barbara, CA 93108
‡Department of Chemistry, Point Loma Nazarene University, San Diego, CA 92106

N-Substituted Oxazolidinones and Amino Alcohols in the Preparation of Functionalized Chiral Auxiliaries

Wittig reagents with chiral auxiliaries can be used to stereoselectively synthesize useful organic compounds. Wittig reagents are used in a reaction with aldehydes or ketones to form carbon-carbon double bonds. The resulting alkenes can be transformed in stereoselective ways using organometallic reagents to produce useful organic compounds. N-substituted oxazolidinones were used to produce Wittig reagents with an ester linkage to a chiral auxiliary. Two novel chiral N-substituted oxazolidinones and one previously synthesized oxazolidinone were used. When an N-tosyl substituted oxazolidinone was used, the Wittig reaction occurred as expected to yield a chiral enoate with a 95:5 E/Z ratio. Using the N-mesitoyl substituted oxazolidinone, the Wittig olefination occurred with a 99:1 E/Z ratio. An alternative method was also employed, by first directly protecting the nitrogen of an amino alcohol and then forming the chiral enoate. This alternate procedure was seen to produce a better product yield in a shorter synthetic process.
Aleah Bond ’14 and David F. Marten, Professor of Chemistry

Turn Sequence Requirements for the Self-assembly of Helix-turn-helix Peptides into α-Helical Fibrils

Apolipoprotein A-I (apo A-I) is the main component of high density lipoprotein (HDL) and is essential in the reverse transport of cholesterol and in the anti-inflammatory properties of HDL. Peptides modeled after apo A-I have been shown to mimic the physical and the functional properties of the full-length protein. Previously, peptide 1, a helix-turn-helix peptide with two identical 18-residue, amphiphilic a-helical segments joined by a turn from apo A-I, was synthesized. This peptide readily formed a-helical fibrils in solution. To investigate the driving forces behind fibril formation, modifications were made to the turn sequence of peptide 1. The effects of these modifications will be explored. The kinetics of fibril formation will also be revealed using intrinsic tryptophan fluorescence. 
Harmeet Takhar ’14, Tjitske Veldstra ‘14, Aaron Barnes’11,Kristi Lazar Cantrell, Assistant Professor of Chemistry

Synthesis and Characterization of Ru(bpy)2-4-(2-phthalimidyl ethyl)-1-10-phenanthroline.

This project was inspired by the study of dendrimers and their use in removing waste water contaminants such as perchlorates and nitrates. Dendrimers are large branches molecules and are capable of binding and reducing these contaminants to less harmful substances with the aid of a Ruthenium metal complex. However, attaching the Ruthenium complex to the dendrimer proved difficult because the Ruthenium complex's reactive amine group (R-NH2) was stabilized from the aromatic ring. An ethyl group was placed between the amine and the aromatic ring to enhance reactivity and coupling to the dendrimer, resulting in Ru(bpy)2-4-(2-phthalimidyl ethyl)-1-10-phenanthroline. The goal of this project was to clean up the synthesis of this molecule, increase the yield, decrease time required for synthesis, and to characterize its reaction intermediates.
Jeremy Kubiak '14, Stephen M. Contakes, Assistant Professor of Chemistry

Preparation of Chiral Cinnamoyl Esters from Cyclic Carbonates

Many biological molecules are chiral, and therefore, many pharmaceuticals are required to be chiral in order to be effective. An ester with a chiral auxiliary attached can be used in stereoselective synthesis. Chiral esters can be synthesized using Wittig reagents that are prepared from cyclic carbonates containing one or more chirality centers. The Wittig reagent is then reacted with benzaldehyde to form the chiral cinnamoyl ester. However, this method has not been found to produce high yields of the trans isomer of the ester. Significant amounts of the cis isomer and the acetate are also produced. Future work will involve testing a shorter method using cinnamoyl chloride to see if it is more selective for the trans isomer and produces a larger yield.
Becky Winchenbaugh ’15, David Marten Professor of Chemistry

Synthesis and Separation of Sub-stoichiometric Ru-functionalized PAMAM Dendrimers

In hopes of breaking down pollutants in water systems, Generation 2.0 PAMAM Ru(bpy)2(dcbpy) dendrimers were previously synthesized and roughly characterized by taking the ratio of Ruthenium:Dendrimer from UV spectrum. It was shown, however, that all the resulting reaction mixtures were hetergenous mixtures Ru:Dend ratio, and could not be accurately characterized until separated. A FPLC(fast protein liquid chromatography) method was developed in order to separate dendrimers by charge using an ion-exchange column. Resulting fractions were analyzed by NMR to determine Ru:dend ratio, and showed the developed method successfully separated a reaction mixture. Further research will pursue photophysically characterizing the separated G2.0 dendrimers and developing a FPLC method to separate G1.5 PAMAM Ru(bpy)2(dcbpy) dendrimers.
Garrett W. Johnson '12, Jeffrey T. Kuwahara '11,Anneka E. Rienstra '15,Tamara Sparks '13, Michelle Haas '11, Elizabeth Grossman '14, Jonas Marks '12, Stephen M. Contakes, Assistant Professor of Chemistry"