Correlation of structure and vibrational spectra of the zwitterion L-alanine in the presence of water: an experimental and density functional analysis.

Infrared vibrational spectra were collected along with the vibrational circular dichroism (VCD) spectra for the zwitterions alpha-D-alanine, alpha-L-alanine, alpha-D-mannose and alpha-L-mannose as potassium bromide (KBr) pressed samples. VCD for D- and L-alanine dissolved in water was also measured and compared against the spectra resulting from KBr pressed samples. The experimental data were compared against the ab initio B3LYP/6-31G* optimized geometry. The zwitterion structure of alpha-L-alanine was stabilized by the addition of water molecules. Computationally, beta-L-mannose was studied and resulting expected VCD bands assigned. We present the molecular structures resulting VCD spectra and infrared vibrational spectra from experimentation as compared with the computed results.