The gas-phase reactions of the allenyl anion with CS2, COS and CO2

The allenyl anion reacts readily in the gas phase with CS2 and COS to form the thioketenyl anion. The reaction involves a complex series of cyclization and ring-opening reactions in which the central carbon of allene and the carbon of the neutral reagent become equivalent. Despite the complexity, the reaction with CS2 is useful in determining the site of deprotonation of unsymmetrical allenes. The reaction of the allenyl anion with CO2 produces only an adduct, because the cleavage reaction to the ketenyl anion and ketene is endothermic. However, the allenyl anion is produced if the reaction is carried out in the reverse direction. (C) 1997 Elsevier Science Ltd.