Chlorination and oxychlorination of aromatic compounds

Direct halogenation is the substitution of a hydrogen atom by a halogen atom, or the addition of halogen or halogenated hydracide to a multiple bond. Aromatic chlorination mainly involves the substitution of a hydrogen atom by a chlorine atom.

The aim of this article is to describe the mechanisms of direct chlorination of aromatic derivatives, chlorinating agents and their industrial implementation: reagents and operating conditions for the main continuous and batch processes.

Over the last twenty years, few new processes have emerged, but the long-standing trend has been towards increasingly high-capacity, highly-automated industrial production units.

In addition, new ecological data concerning chlorinated products are forcing manufacturers to eliminate the various sources of pollution and to recycle or recover their waste. For these reasons, the importance of certain processes is declining in favor of more efficient and selective ones.

The chlorinated products thus obtained, mainly from benzene and toluene, lead to synthesis intermediates used in the dye, pharmaceutical and pesticide industries.