Determination of Reactivity by MO Theory (Part 50). MO Studies on the Gas Phase Pyrolysis of Esters

摘要

The gas phase pyrolyses of eight esters have been studied by MNDO-MO method. In the ethylformate pyrolysis, メ-methylation had a steric releasing effect whereas モ-methylation had a steric crowding in the transition state; the latter, however, is over-compensated by a greater electronic repulsion resulting in a net steric releasing effect. Considerations of formal charges and geometrical changes involved in the activation led us to propose a pyrolysis mechanism in which a preequilibrium of acidic proton transfer is followed by the rate-limiting bond polarization of Cメ-O bond in a cyclic transition state.