Rearrangement of the Fulminate Anion (CNO^-) to the Cyanate Anion (OCN^-). Possible Intermediacy of the Oxazirinyl Anion

Abstract

The rearrangement of the fulminate anion (CNO^-) to the cyanate anion (OCN^-) has been examined by using high-level ab initio molecular orbital calculations which include a diffuse-function-augmented polarization basis set and electron correlation incorporated at the full fourth-order Moller-Plesset level (MP4). The reaction is predicted to be exothermic by 275 kJ mol^-1. Our best calculations indicate theinvolvement of a metastable cyclic oxazirinyl anion intermediate. However, this lies in an extremely shallow potential well and, in contrast to the predictions of semiempirical calculations, is unlikely to have more than a fleeting existence. The fulminate and cyanate anions are calculated to be stable with respect to electron loss and stable with respect to intramolecular rearrangement; accordingly, both should be observable gas-phase species.