Nuclear chlorination of toluene

Chlorination of the aromatic nucleus is generally carried out at relatively low temperatures (ca. 50 °C) under atmospheric pressure, yielding ca. 95% monochloro-toluene and 5% dichlorotoluenes the proportions of 2- and 4-chlorotoluene can 

4-Chlorotoluene is of particular importance, with a production in Western Europe in 1985 of around 20,0001. The most important product from 4-chloro-toluene is 4-chlorobenzotrichloride, which is produced by photochlorination. 

It serves as an intermediate in, e.g., the production of 4-chlorobenzotrifiuoride, which is further processed to manufacture the plant protection agent trifluralin. Nucleophilic substitution of 4-chloro-3,5-dinitrobenzotrifluoride with di-n-propyl-amine leads to trifluralin. 

World production of this pre-emergence herbicide, developed by Eli Lilly, is around 25,000 tpa. 

Another plant protection agent based on 4-chlorotoluene is fenvalerate (see Chapter 5.3.4.3.1), which works in a similar way as pyrethroid insecticides. 

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