Structure and fragmentation of glycine, alanine, serine and cysteine radical cations. A theoretical study

The structure of glycine, alanine, serine and cysteine radical cations, as well as their Ca–R fragmentations have been studied at the B3LYP/6-31CCG(d,p) level of theory. For all systems the loss of COOH is found to be the most favourable process. However, when R1 size increases, fragmentations that lead to R1 % or R1 start become competitive. The energy of a Ca–R fragmentation can be related to the ionization potential of the two generated fragments, in such a way that the preferred process is the one that leaves the positive charge in the fragment with a lower ionization potential. q 2005 Elsevier B.V. All rights reserved.