Isomerization versus Fragmentation of Glycine Radical Cation in Gas Phase

The isomerization and fragmentation reactions of glycine radical cation, [NH 2 CH 2 COOH] +•, have been studied using the B3LYP density functional approach and the post-Hartree−Fock CCSD(T) method. The most stable isomer of glycine radical cation corresponds to [NH 2 CHC(OH) 2 ] +• . The isomerization reaction from ionized glycine, [NH 2 CH 2 COOH] +•, to [NH 2 CHC(OH) 2 ] +• presents a high energy barrier due to large geometrical distortions at the transition state and important electronic reorganization. In contrast, the fragmentation processes arising from the C α −R cleavage NH 2 CH 2 COOH +• → NH 2 CH 2 + + COOH • and NH 2 CH 2 COOH +• → NH 2 CHCOOH + + H • appear to be more favorable. The effect of solvation on the isomerization and fragmentation reactions is discussed.