A density functional theory study of the radiation products of glycine

Density functional theory was employed to investigate: the radicals that ha ve been proposed to be formed upon irradiation of glycine crystals. The pre sent theoretical study suggests that the radicals are R1: (+NH3CHCOO-)-H-.; R2: (CH2COOH)-C-.; R3: (NH2CHCOOH)-H-.; and R3: (NH2CH2COCHCOOH)-H-.. A C- s structure for Ri, obtained using the Onsager model, gives hyperfine coupl ing constants in agreement with experiment. Hyperfine coupling constants co mputed for R2 are in agreement with the unassigned experimental data of Tes lenko. V. V. et al. (Mol. Phys. 1975, 30, 425). The computed hyperfine coup ling constants for R4 are in good agreement with the experimental data assi gned to the zwitterionic form (+NH3CH2COCHCOO-)-H-. It is shown that the st ructure of R3 is influenced significantly by the glycine crystal environmen t. Protonation of R3 gives rise to hyperfine couplings similar to the exper imental values assigned to one conformer of R3.