The gas phase ion/molecule chemistry of four carbanions generated from vinylene carbonate and its methyl and dimethyl derivatives

Abstract

The gas phase ion/molecule chemistry of four carbanions generated by the reaction of vinylene carbonate, ▪ and its methyl and dimethyl derivatives with hydroxide ion has been investigated. From the parent the sole product is the ketenyl anion, HCCO −, arising from vinylic proton abstraction and loss of CO 2. From the dimethyl derivative, abstraction of an allylic proton from one of the methyl groups followed by loss of CO 2 leads exclusively to CH 2CC(O)CH 3. Both pathways are observed for the monomethyl derivative, leading to a mixture of the ions CH 3CCO − and CH 2CCHO. The ketenyl and methyl ketenyl ions do not exchange hydrogen for deuterium with D 2O or CH 3OD, but they do react with CS 2 and COS to form the corresponding thioketenyl anions, HCCS − and CH 3CCS −. The ions CH 2CC(O)CH 3 and CH 2CCHO exchange one and three hydrogen atoms for deuterium atoms with D 2O respectively, and react with CS 2 to form thioketenyl anions by addition and loss of thioformaldehyde. Possible mechanisms for these reactions are discussed.