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

The gas phase ion/molecule chemistry of four carbanions generated by the reaction of vinylene carbonate, {A figure is presented} and its methyl and dimethyl derivatives with hydroxide ion has been investigated. From the parent the sole product is the ketenyl anion, HCCO^-, arising from vinylic proton abstraction and loss of CO₂. From the dimethyl derivative, abstraction of an allylic proton from one of the methyl groups followed by loss of CO₂ leads exclusively to CH₂CC(O)CH₃. Both pathways are observed for the monomethyl derivative, leading to a mixture of the ions CH₃CCO^- and CH₂CCHO. The ketenyl and methyl ketenyl ions do not exchange hydrogen for deuterium with D₂O or CH₃OD, but they do react with CS₂ and COS to form the corresponding thioketenyl anions, HCCS^- and CH₃CCS^-. The ions CH₂CC(O)CH₃ and CH₂CCHO exchange one and three hydrogen atoms for deuterium atoms with D₂O respectively, and react with CS₂ to form thioketenyl anions by addition and loss of thioformaldehyde. Possible mechanisms for these reactions are discussed.