Date Thesis Awarded
5-2011
Access Type
Honors Thesis -- Access Restricted On-Campus Only
Degree Name
Bachelors of Science (BS)
Department
Chemistry
Advisor
John C. Poutsma
Committee Members
Christopher J. Abelt
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.
Recommended Citation
Yannello, Vincent James, "Gas-Phase Thermochemistry of Non-Protein Amino Acids by the Extended Kinetic Method" (2011). Undergraduate Honors Theses. William & Mary. Paper 401.
https://scholarworks.wm.edu/honorstheses/401
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.