Ab initio quantum-chemical study of the reaction mechanisms of acetylene in superbasic media. Noncatalytic vinylation of methanol

Abstract

The reaction profile of noncatalytic vinylation of methanol with acetylene was studied by ab initio quantum-chemical calculations for the gas phase and by calculations using a combined model that took into account the solvent (DMSO) effect. The reaction occurs via the formation of a prereaction complex of the methoxide ion with acetylene; at this stage, the acetylene molecule is already activated with respect to the proton. The observed stereospecific trans-addition in methanol vinylation in the gas phase and solution is provided by the lower activation barrier corresponding to the E structure of the acetylene molecule in the transition state and barrier-free protonation of the carbanion intermediate.