PNNL

Abstract

Ab initio calculations of the geometry and reactivity of 1,2-ketocarbene C6H4O as an intermediate in organic reactions were performed using the second-order Møller-Plesset (MP2) perturbation theory in the 6-311G* basis set. Only the singlet state of the intermediate was considered. An oxirene-like structure (6) with a six-membered ring and a ketene-like structure (5) with a five-membered ring were localized on the potential energy surface. Attempts to locate a quinone type structure characteristic of aliphatic ketocarbenes failed. The energy of structure5 is -70 kcal mol-1 lower than that of structure6. Harmonic frequencies and intensities of normal vibrations in the IR spectra of6 and5 were calculated. The activation energy of the Wolff rearrangement6?5 was estimated at 12.5 kcal mol-1. The geometry of the transition state of this reaction resembles the quinone-like structure.