Abstract: This invention relates to an improved process for producing 2,6-dichloro-3,5-di(secondary or tertiary alkyl)toluene represented by the following formula (I). The process comprises chlorinating 3,5-di(secondary and tertiary alkyl)toluene represented by the following formula (II) by reacting with a chlorinating agent in the presence of a Lewis acid together with an aromatic sulfur compound represented by the formula (III) as a promoter: wherein R1 and R2 are independently a secondary alkyl or tertiary alkyl group, Ar1 and Ar2 are independently an unsubstituted or substituted aromatic ring, and n is 1 or 2.

Abstract: Disclosed herein is a process for producing 2,5-dichlorotoluene which is useful as a monomer of heat-resistant polymers and an intermediate raw material for medicines, agricultrual chemicals and various organic synthetic substances, the process giving 2,5-dichlorotoluene at a high selectivity and in a high yield and comprising the steps of chlorinating 4-t-alkyltoluene or 4-isopropyltoluene in the presence of a catalyst, thereby obtaining a 2,5-dichlorocompound, and bringing the formed 2,5-dichlorocompound into contact with toluene in the presence of a catalyst, thereby subjecting the 2,5-dichlorocompound to transalkylation.