Dihalomethanes

Dihalomethanes are a class of organohalogen compounds consisting of a methane skeleton with two halogen substituents. The general formula is CH2X2, where X is a halogen such as fluorine, chlorine, bromine, or iodine. Common members include difluoromethane (CH2F2), dichloromethane (CH2Cl2), dibromomethane (CH2Br2), and diiodomethane (CH2I2).

Physical properties vary with the halogen identity. Difluoromethane is a gas at room temperature, while the chlorinated and brominated members are volatile liquids; diiodomethane is a dense liquid. They are generally nonpolar or weakly polar and have relatively low boiling points compared with many other organic compounds. They can occur as industrial solvents or reagents and are handled accordingly in chemical processes.

Occurrence and uses often center on solvents and intermediates in organic synthesis. Dichloromethane is a widely used solvent known as methylene chloride, employed in paint stripping, degreasing, and pharmaceutical manufacturing. Difluoromethane is used as a refrigerant (R-32) and as a blowing agent in foam production. Dibromomethane and diiodomethane serve as solvents or reagents in specialized syntheses. Dihalomethanes can also form as byproducts in water treatment and other chlorination processes, contributing to halogenated volatile organic compounds in air and water.

Safety and environmental considerations are important for dihalomethanes. Many members are toxic and may pose health risks upon exposure; regulatory limits exist for occupational and environmental exposure. They are typically volatile and can contribute to air and water pollution; some species may affect aquatic life. Proper handling, ventilation, and waste management are advised in their use and disposal.