eprintid: 14441
rev_number: 29
userid: 1291
dir: disk0/00/01/44/41
datestamp: 2012-09-25 14:21:58
lastmod: 2021-06-12 23:55:16
status_changed: 2012-09-25 14:21:58
type: article
metadata_visibility: show
item_issues_count: 0
eprint_status: archive
creators_name: Bykov, SV
creators_name: Myshakina, NS
creators_name: Asher, SA
creators_email:
creators_email:
creators_email: asher@pitt.edu
creators_id:
creators_id:
creators_id: ASHER
title: Dependence of glycine CH2 stretching frequencies on conformation, ionization state, and hydrogen bonding
ispublished: pub
divisions: sch_as_chemistry
full_text_status: public
abstract: We experimentally and theoretically examined the conformation, pH, and temperature dependence of the CH2 stretching frequencies of glycine (gly) in solution and in the crystalline state. To separate the effects of the amine and carboxyl groups on the CH2 stretching frequencies we examined the Raman spectra of 2,2,2-d3-ethylamine (CD 3-CH2-NH2) and 3,3,3-d3-propionic acid (CD3-CH2-COOH) in D2O. The symmetric (vsCH2) and asymmetric (vasCH2) stretching frequencies show a significant dependence on gly conformation. We quantified the relation between the frequency splitting (Δ = v asCH2 -vsCH2) and the ξ angle which determines the gly conformational geometry. This relation allows us to determine the conformation of gly directly from the Raman spectral frequencies. We observe a large dependence of the vsCH2 and v asCH2 frequencies on the ionization state of the amine group, which we demonstrate theoretically results from a negative hyperconjugation between the nitrogen lone pair and the C-H antibonding orbitais. The magnitude of this effect is maximized for C-H bonds trans to the nitrogen lone pair. In contrast, a small dependence of the CH2 stretching frequencies on the carboxyl group ionization state arises from derealization of electron density from carboxyl oxygen to C-H bonding orbitals. According to our experimental observations and theoretical calculations the temperature dependence of the vsCH2 and v asCH2 of gly is due to the change in the hydrogen-bonding strength of the amine/carboxyl groups to water. © 2008 American Chemical Society.
date: 2008-05-08
date_type: published
publication: Journal of Physical Chemistry B
volume: 112
number: 18
pagerange: 5803 - 5812
refereed: TRUE
issn: 1520-6106
id_number: 10.1021/jp710136c
other_id: NLM NIHMS239071
other_id: NLM PMC2952399
pmcid: PMC2952399
pmid: 18447350
mesh_headings: Amines--chemistry
mesh_headings: Carbon--chemistry
mesh_headings: Glycine--chemistry
mesh_headings: Hydrogen--chemistry
mesh_headings: Hydrogen Bonding
mesh_headings: Ions--chemistry
mesh_headings: Models, Molecular
mesh_headings: Molecular Conformation
mesh_headings: Propionic Acids--chemistry
mesh_headings: Solutions
mesh_headings: Spectrum Analysis, Raman
mesh_headings: Temperature
mesh_headings: Vibration
chemical_names: Amines
chemical_names: Ions
chemical_names: Propionic Acids
chemical_names: Solutions
chemical_names: Hydrogen
chemical_names: Glycine
chemical_names: Carbon
chemical_names: propionic acid
citation: Bykov, SV and Myshakina, NS and Asher, SA (2008) Dependence of glycine CH2 stretching frequencies on conformation, ionization state, and hydrogen bonding. Journal of Physical Chemistry B, 112 (18). 5803 - 5812. ISSN 1520-6106
document_url: http://d-scholarship-dev.library.pitt.edu/14441/1/licence.txt