Isomerization versus fragmentation of glycine radical cation in gas phase

The isomerization and fragmentation reactions of glycine radical cation, [NH2CH2COOH](+.), 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 [NH2CHC(OH)2](+.). The isomerization reaction from ionized glycine, [NH2CH2COOH](+.), to [NH2CHC(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-alpha-R cleavage NH2CH2COOH+. --> NH2CH2+ + COOH. and NH2CH2COOH+. --> NH2CHCOOH+. + H-. appear to be more favorable. The effect of solvation on the isomerization and fragmentation reactions is discussed.