Date Thesis Awarded

5-2008

Document Type

Honors Thesis

Degree Name

Bachelors of Science (BS)

Department

Chemistry

Advisor

John C. Poutsma

Committee Member

Robert D. Pike

Committee Member

Lisa M. Landino

Committee Member

Marc Sher

Abstract

The gas-phase acidities and proton affinities of analogs of protein amino acids were investigated. The gas-phase acidities of the lysine homologues were measured by the extended kinetic method in a quadrupole ion trap mass spectrometer. Deprotonation entropy changes were also measured. For ornithine, 2,4-diaminobutyric acid, and 2,3-diaminopropionic acid, the gas-phase acidities measured were 1416 ± 17 kJ/mol, 1420 ± 8 kJ/mol, and 1405 ± 24 kJ/mol. Their changes in entropy were measured to be -19 J/mol K, 1 J/mol k, and -24 J/mol K, respectively. The gas-phase acidities and entropies of two structural analogs of arginine, citrulline and canavanine, were measured by the extended kinetic method. The gas-phase acidity of citrulline was measured to be 1366 ± 11 kJ/mol, and the gas-phase acidity of canavanine was measured to be 1401 ± 13 kJ/mol. The proton affinity and protonation entropy change for citrulline was measured as well. The proton affinity was determined to be 984 ± 11 kJ/mol with an entropy change of -6 J/mol K. The proton affinity and protonation entropy change of L-BMAA, a structural analogue of alanine and 2,3-diaminopropionic acid, was measured by the extended kinetic method to be 960 ± 7 kJ/mol. The entropy for the protonation reaction was found to be -4 J/mol K. Hybrid density functional theory calculations were performed on the compounds examined. Energy-optimized geometries were examined for structural trends and theoretical predictions for the gas-phase acidities and proton affinities were made. The experimental and theoretical determinations reveal the effects of structural changes on gas-phase thermochemical properties.

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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