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How are dichloromethane and chloroform made through chlorination reactions?

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organohalogen compound Vinyl chloride is an organohalogen compound that has important industrial applications. When treated with certain catalysts, vinyl chloride monomers undergo polymerization and form the larger compound known as polyvinyl chloride, or PVC. PVC is used in the manufacture of numerous products, including packaging films and water pipes.

Dichloromethane and chloroform are produced through the sequential free-radical chlorination of methane derivatives.1

Dichloromethane (methylene chloride) is prepared by the chlorination of chloromethane.12
Chloroform (trichloromethane) is prepared by the chlorination of dichloromethane.1

These processes are part of a broader series of reactions involving the chlorination of methane. The initial step in this sequence is the synthesis of chloromethane, which can be achieved through high-temperature gas-phase chlorination of methane. This reaction is a free-radical process that can be initiated by light or ultraviolet radiation, involving a chain mechanism where chlorine atoms react with methane to produce methyl radicals, which subsequently react with chlorine molecules to form the product.13

While chloromethane is also commonly produced by reacting methanol with hydrogen chloride, the subsequent production of dichloromethane and chloroform relies on the continued chlorination of the preceding chlorinated methane species.12