Vibrational spectra of acid and alkaline glycine salts

Abstract

The infrared and Raman spectra of crystalline acid (+NH3CH2COOH·Cl−) and alkaline (Na+·NH2CH2COO−) glycine salts were recorded and interpreted. The assignments were confirmed by comparison with the infrared and Raman spectra of crystalline glycine (zwitterion, +NH3CH2COO−) and the infrared spectrum of this molecule isolated in an argon matrix at low temperature (10 K) (neutral form, NH2CH2COOH). Further insight on the features of the vibrational spectra of these substances was achieved by ab initio (HF/6-31G*) frequency and intensity calculations and potential energy distribution calculations resulting from normal coordinate analysis.