A Density Functional Theory Study of the Radiation Products of Glycine

Density functional theory was employed to investigate the radicals that have been proposed to be formed upon irradiation of glycine crystals. The present theoretical study suggests that the radicals are R1: + NH 3 C • HCOO -; R2: • CH 2 COOH; R3: NH 2 C • HCOOH; and R4: NH 2 CH 2 COC • HCOOH. A C s structure for R1, obtained using the Onsager model, gives hyperfine coupling constants in agreement with experiment. Hyperfine coupling constants computed for R2 are in agreement with the unassigned experimental data of Teslenko, V. V. et al. ( Mol. Phys . 1975, 30, 425). The computed hyperfine coupling constants for R4 are in good agreement with the experimental data assigned to the zwitterionic form + NH 3 CH 2 COC • HCOO - . It is shown that the structure of R3 is influenced significantly by the glycine crystal environment. Protonation of R3 gives rise to hyperfine couplings similar to the experimental values assigned to one conformer of R3.