KINETICS OF THE CHLORINATION OF ACETIC-ACID WITH CHLORINE IN THE PRESENCE OF CHLOROSULFONIC ACID AND THIONYL CHLORIDE

The chlorination of acetic acid with molecular chlorine in the presenc e of chlorosulfonic acid and thionyl chloride as catalytic agents was studied in a laboratory-scale semibatch reactor operating at atmospher ic pressure. Monochloroacetic acid was the main product, and dichloroa cetic acid was formed in parallel as a byproduct. Chlorosulfonic acid was a more active catalytic agent than thionyl chloride owing to its a cid catalytic effect in enolization of the real catalytic intermediate , acetyl chloride. When the whole amount of the catalytic agent was in troduced in the beginning of the reaction decreasing chlorination rate s were observed, whereas autocatalytic kinetics appeared when stepwise addition of the catalytic agents was applied. In the former case the decreasing reaction rates were explained by the decomposition of the c atalytic agents following first-order kinetics. The autocatalytic effe cts were explained by a kinetic model involving acid-catalyzed enoliza tion of acetyl chloride and chlorination of the enol as rate-determini ng steps. The kinetic model provided a good description of the experim ental results.