THE WOLFF REARRANGEMENT - THE RELEVANT PORTION OF THE OXIRENE-KETENE POTENTIAL-ENERGY HYPERSURFACE

The portion of the C2H2O potential energy hypersurface that includes o xirene, formylmethylene, and ketene has been studied with ab initio me thods incorporating high levels of electron correlation and basis sets that include up to f and g functions. Our best geometries were determ ined at the CCSD(T)/6-311G(df,p) level of theory. Single-point energie s were then determined by using CCSD(T) and BD(T) calculations with th e cc-pVTZ basis set augmented with additional f and g polarization fun ctions. Our main conclusion is that there is little or no barrier sepa rating formylmethylene from oxirene, the potential energy surface link ing these two species being extremely flat. On the other hand, a more significant barrier (21-23 kJ mol(-1)) separates formylmethylene or ox irene from ketene. These results strongly support the previously postu lated intermediacy of oxirene in the Wolff rearrangement. Ketene is fo und to lie 325 kJ mol(-1) lower in energy than oxirene. Our predicted energy threshold for the scrambling of carbon atoms in ketene (348 kJ mol(-1)) is in close agreement with a recent experimental value (340 k J mol(-1)).