1,3-Dichlorobenzene is an organic compound with the formula C6H4Cl2. It is the least common of the three isomers of dichlorobenzene, it is a colorless liquid that is insoluble in water. It is produced as a minor byproduct of the chlorination of benzene, but can also be prepared in a directed manner by the Sandmeyer reaction of 3-chloroaniline. It also arises from the isomerization of the other dichlorobenzenes at high temperature.Used in organic synthesis. The Friedel-Crafts reaction between m-dichlorobenzene and chloroacetyl chloride yields 2,4,ω-trichloroacetophenone, which is used as an intermediate for the broad-spectrum antifungal drug miconazole. The chlorination reaction is carried out in the presence of ferric chloride or aluminum mercury, and 1,2,4-trichlorobenzene is mainly produced. In the presence of a catalyst, it is hydrolyzed at 550-850°C to produce m-chlorophenol and resorcinol. Using copper oxide as a catalyst, it reacts with concentrated ammonia at 150-200°C under pressure to generate m-phenylenediamine. 2. Used in dye manufacturing, organic synthesis intermediates and solvents.