Semiempirical calculations on the ring opening of α-lactones

We report the results of INDO calculations on the ring opening of acetolactone and its difluoro and dimethyl derivatives. Of the structures possibly important in the chemistry of α-lactones, the closed system is most stable. The open form, which we call methylenecarboxylate, is calculated by the INDO method to be more stable as a triplet. Finally a semi-open structure, favored in the older literature, is predicted to be chemically unimportant.