Chlorobenzene

Chlorobenzene is an aromatic organic compound with the chemical formula C6H5Cl. It is a colorless, flammable liquid first made in 1851 by reacting phenol and phosphorus pentachloride.

Uses
Chlorobenzene has been used in the manufacture of certain pesticides, most notably DDT by reaction with chloral (trichloroacetaldehyde). It once found use in the production of phenol. Today the major use of chlorobenzene is as an intermediate in the production of nitrochlorobenzenes and diphenyl oxide, which are important in the production of commodities such as herbicides, dyestuffs, and rubber. Chlorobenzene is also used as a high-boiling solvent in organic synthesis as well as many industrial applications.

Synthesis
Chlorobenzene is prepared by chlorination of benzene, usually in the presence of a catalytic amount of Lewis acid such as ferric chloride:
 * C6H6 + Cl2 &rarr; C6H5Cl + HCl

Because chlorine is electronegative, PhCl exhibits decreased susceptibility to attack by other electrophiles. For this reason, the chlorination process produces only small amounts of dichloro- and trichlorobenzenes.