The hydorgen-transfer mechanisms of β-hydroxy propaldehyde at the ground-state and the exited-state potential energy sufaces have been intensively investigated by performing ab initio RHF/3-21G and UHF/3-21G calculations. At the ground-state potential energy surface, β-hydroxy propaldehyde molecule can dissociate into the ground state H2CO and CH2CH(OH) via a six-memebered cyclic transition state and a hydrogen-bonded complex intermediate. This reaction is a concerted process with hydrogen-transfer and bond-breaking. At the exited-state potential energy surface, the exited-state (n→π^*) β-hydroxy propaldehyde firstly forms a biradical intermediate via a six-membered cyclic transition state, then there are two competitive processes for the decomposition from this intermediate. One is to form ground-state H2CO and exited-state CH2CH(OH) via a transition state with C-C bond breaking and an intermediate with hydrogen-bond. The other is to form exited-state H2CO and ground-state CH2CH(OH) via a similar transition state and an intermediate. The reactions for the exited-state are stepwise processes with hydrogen-transfer and bond-breaking orderly. And the second step is the rate determing step. The activation barriers for the exited-state reactions are lower than that of the ground-state.

Key words: REACTION MECHANISM, FORMALDEHYDE, AB INITIO CALCULATION, GROUND STATE, PROPANAL P, VINYL ALCOHOL, MIGRATION MECHANISM