Date Thesis Awarded

5-2011

Document Type

Honors Thesis

Degree Name

Bachelors of Science (BS)

Department

Chemistry

Advisor

John C. Poutsma

Committee Member

Christopher J. Abelt

Committee Member

Rex K. Kincaid

Abstract

In this study, we have been examining the gas-phase acidities of two amino acid homologues, homocysteine and homoserine, and the proton affinity of another amino acid homologue, homohomoserine. Homocysteine, homoserine, and homohomoserine are non-protein amino acids (NPAA) that have very similar structures to the protein amino acids (PAA) cysteine and serine. The gas-phase acidities of both cysteine and serine are well known and an analysis of the gas-phase basicity of their homologues has yielded information regarding the effects of small changes in structure on a basic physical property. Similarly, the proton affinities of serine and homoserine are well-known, so investigating the proton affinity of the next homologue has yielded more information as well. To do this experiment, we used a triple quadrupole mass spectrometer with an electrospray ionization source and utilized the kinetic method. In this method, the gas-phase acidity of the compound of interest is determined by comparing it to other compounds of known gas-phase acidity, called reference acids, inside the mass spectrometer. A proton-bound dimer is formed and is collided with an inert gas at various energies to obtain a kinetic plot. This is repeated for multiple reference acids and an intersection is found. This intersection is the gas-phase acidity of the compound of interest. A similar analysis was done for the proton affinity of homohomoserine. The final values obtained were 1394.6 ± 10 kJ/mol for the gas-phase acidity of homoserine, 1392.8 ± 10 kJ/mol for the gas-phase acidity of homocysteine, and 968.7 ± 10 kJ/mol for the proton affinity of homohomoserine.

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

Comments

Thesis is part of Honors ETD pilot project, 2008-2013. Migrated from Dspace in 2016.

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