A theoretical study of the Norrish type I reaction of acetone

Abstract

The α-cleavage (Norrish type I) reaction of acetone in excited states has been theoretically studied. The potential energy surfaces participating in the dissociation (S 0, S 1 and T 1 states) were calculated with the complete active space (CAS) SCF method and the effect of dynamic electron correlation was taken into account by the second-order multi-reference Møller–Plesset perturbation (MRMP2) method. It is shown that the MRMP2 calculations improve the potential energy features though the dissociation energy in the S 0 state is still underestimated. The calculated potential barrier for the dissociation on the T 1 surface was comparable to the experimental value. Rice–Ramsperger–Kassel–Marcus (RRKM) calculations were performed to estimate the rate constant with the use of potential parameters derived from the present ab initio calculations. The calculated rate constant was compared to the available experiments. Some of the experimentally measured lifetimes are consistent with the calculated ones, while there is a large discrepancy between the most recent experiment for the S 2 state and the present RRKM result.