Multi-channel reactions of intramolecular proton transfer on serinamide in the ground and excited states: A theoretical study

Abstract

Multi-channel reactions of intramolecular proton transfer on serinamide in the ground state and excited state have been determined by studying five pairs of mirror-image conformers of serinamide in excited state and eight pairs in ground state. Density function theory calculations have been made at B3LYP/6-311++G** level. Four different channels for intramolecular proton transfer are confirmed by theoretical calculations for the excited and ground states. For the excited state intramolecular proton transfer, process CH2 (H10 from CH to O2) is considered to be the most favorable channel with the lowest energy barrier (Ea = 86.267 kJ/mol). At the same time, process CH1 (H9 from N3 to O2) is calculated to be both thermodynamically and kinetically favored for the ground state intramolecular proton transfer. Comparing the activation energies of these channels, it may be inferred that the activation energy needed by the excited state intramolecular proton transfer process is much lower than that required by ground state intramolecular proton transfer process. Therefore, intramolecular proton transfer reaction processes in excited state are much easier than those in ground state.