Ab Initio Study and Nbo Analysis of the Unimolecular Decomposition Kinetics of 2,2-Dimethyloxetane

Abstract

Theoretical study of the thermal decomposition kinetics of 2,2-dimethyloxetane has been carried out at the B3LYP/6-311 + G**, B3PW91/6-311 + G**, and MPW1PW91/6-311 + G** levels. The MPW1PW91/6-311 + G** method was found to give a reasonably good agreement with the experimental kinetics and thermodynamic parameters. Two parallel unimolecular reactions occur to give either isobutene and formaldehyde [reaction (1)] or ethene and acetone [reaction (2)]. The calculated data demonstrate that the polarization of the O1-C2 bond in reaction (1) and C4-O1 bond in reaction (2), are rate determining. The analysis of bond order and NBO charges, bond indices, synchronicity parameters, and IRC calculations suggest reactions (1) and (2) occur through a concerted and asynchronous four-membered cyclic transition state type of mechanism.