Mechanistic study on metal-free acetylene hydrochlorination catalyzed by imidazolium-based ionic liquids

A novel green approach to acetylene hydrochlorination yielding vinyl chloride is presented using 1-alkyl-3-methyimidazolium-based ionic liquids (ILs) as single component metal-free catalysts. The effects of anion species and substituent group in the imidazolium cation on the reaction are investigated. Through the catalytic performance and computational simulation, the catalytic mechanism of single component ILs for metal-free acetylene hydrochlorination is proposed. It is suggested that ILs as single component metal-free catalysts must consist of chloride anion, which is participate in the reaction process of acetylene hydrochlorination to form [HCl2]− through the activation of HCl molecule. Notably, the structural modification of conjugated cation will be the key factor to further improve the catalytic efficiency. The mechanistic understanding has an important significance to modify the metal-free catalytic efficiency of ILs for acetylene hydrochlorination.