Cycloaddition of acrylonitrile to allene: computed reaction path (AM1) and intramolecular secondary isotope effect

Abstract

The reaction path for cycloaddition of acrylonitrile to allene was computed using the AM1 Hamiltonian with limited configuration interaction (C.I. = 4). Cycloaddition is found to proceed stepwise via a biradical intermediate, in confirmation of the conclusion reached by Dolbier and Dai on the basis of the intramolecular and intermolecular H/D kinetic isotope effects on the reaction. A transition state theory calculation of the ratio of the two isotopomeric products obtained from cycloaddition of acrylonitrile with gem-dideuteroallene is in good agreement with the experimental observations. A parallel set of computations on the cycloaddition of fluoroethylene to allene yielded similar results.