Structures, Energetics and Vibrational Frequencies of Cyclopropyne

Abstract

AbstractThe electronic structure of the lowest singlet and triplet states of cyclopropyne have been investigated using ab initio molecular quantum mechanics. Both double zeta (DZ) and double zeta plus carbon d function (DZ + d) basis sets have been used in conjunction with self‐consistent‐field (SCF), multiconfiguration (MC) SCF, and configuration interaction (CI) methods. Singlet cyclopropyne is predicted to be a transition state for the degenerate rearrangement of propadienylidene (H2C=C=C:). However, triplet cyclopropyne is a minimum on the C3H2 potential energy hypersurface and vibrational frequencies are predicted at two levels of theory. Structures and vibrational frequencies are compared with those of the relatively stable cyclopropene molecule.