Methylene Chloride

Methylene Chloride

Dichloromethane (DCM, methylene chloride, or methylene bichloride) is an organochlorine compound with the formula CH2Cl2. This colorless, volatile liquid with a chloroform-like, sweet odor is widely used as a solvent. Although it is not miscible with water, it is slightly polar, and miscible with many organic solvents.[12]

Occurrence

Natural sources of dichloromethane include oceanic sources, macroalgae, wetlands, and volcanoes.[13] However, the majority of dichloromethane in the environment is the result of industrial emissions.[13]

Production

DCM is produced by treating either chloromethane or methane with chlorine gas at 400–500 °C. In this way, an estimated 400,000 tons were produced in the US, Europe, and Japan in 1993.[12]

CH4 + Cl2 → CH3Cl + HCl

CH3Cl + Cl2 → CH2Cl2 + HCl

CH2Cl2 + Cl2 → CHCl3 + HCl

CHCl3 + Cl2 → CCl4 + HCl

The output of these processes is a mixture of chloromethane, dichloromethane, chloroform, and carbon tetrachloride as well as hydrogen chloride as a byproduct. These compounds are separated by distillation.

DCM was first prepared in 1839 by the French chemist Henri Victor Regnault (1810–1878), who isolated it from a mixture of chloromethane and chlorine that had been exposed to sunlight.[14]

Uses

DCM's volatility and ability to dissolve a wide range of organic compounds makes it a useful solvent for many chemical processes.[12] In the food industry, it is used to decaffeinate coffee and tea as well as to prepare extracts of hops and other flavourings.[15][16] Its volatility has led to its use as an aerosol spray propellant and as a blowing agent for polyurethane foams.

Specialized uses

Near IR absorption spectrum of dichloromethane showing complicated overlapping overtones of mid IR absorption features

The chemical compound's low boiling point allows the chemical to function in a heat engine that can extract mechanical energy from small temperature differences. It is also used as the fluid in jukebox displays and holiday bubble lights.heat and a small amount of rock salt to provide thermal mass and a nucleation site for the phase changing solvent.

DCM chemically welds certain plastics. For example, it is used to seal the casing of electric meters. Often sold as a main component of plastic welding adhesives, it is also used extensively by model building hobbyists for joining plastic components together. It is commonly referred to as "Di-clo".

It is used in the garment printing industry for removal of heat-sealed garment transfers.

Dichloromethane extract of Asparagopsis taxiformis, a seaweed fodder for cattle, has been found to reduce their methane emissions by 79%.[19]