Chlorination of Methylcyclohexane in Molten Salt Media

Abstract

The chlorination of methylcyclohexane in several molten metal chloride mixtures (ZnCl₂/KCl/NaCl, CuCl/ KCl/NaCl, AlCl₃/KCl/NaCl, and CuCl₂/KCl/NaCl) has been carried out, using nitrogen gas as a diluent, at three levels of temperature (250, 350, and 450°C. The reactions in both ZnCl₂ and CuCl melts were studied extensively, the former representing the molecular-type melt and the latter standing for the partially-ionic-type one. These reactions gave 1-, 2-, 3-, and 4-chloro-methylcyclohexanes and 1-, 3-, and 4-methylcyclohexenes as primary products, along with smaller amounts of toluene and methylcyclohexadiene. The formation of these olefins were interpreted by the subsequent elimination (by a carbonium-ion mechanism) of HCl catalytically enhanced by these melts from the methyl-chlorocyclohexane derivatives. The difference observed in the product distributions between ZnCl₂ and CuCl melts was also explained by the studies of the effect of hydrogen chloride produced in these reactions over molten salts.