What Is Dichloromethane?
Dichloromethane (DCM), also known as methylene chloride or methylene dichloride, is a colorless liquid noted for its strong, sweet aroma. It may cause mild irritation or chemical injury upon skin contact. Due to its anesthetic vapor, inhaling large quantities quickly can lead to acute poisoning, necessitating caution during use. DCM is produced by chlorinating methyl chloride or by reducing chloroform with zinc and acetic acid.
Uses of Dichloromethane
Dichloromethane finds broad industrial applications as a refrigerant, cleaning agent for metal equipment and printed circuit boards, foaming aid for urethane, paint stripper, and aerosol propellant. It is a preferred solvent for organic substances due to its low boiling point and high purity requirements. Additionally, dichloromethane is used in manufacturing polycarbonates, pharmaceuticals, agrochemicals, and precision analysis like liquid chromatography.
It is favored over other halogenated hydrocarbons due to its nonflammability, lower toxicity, and as an alternative to trichloroethylene.
Properties of Dichloromethane
With a chemical formula of CH2Cl2, DCM’s structure consists of two chlorine atoms replacing two hydrogen atoms in methane. It has a density of 1.3266 g/cm³, a melting point of -96.7°C, and a boiling point of 40°C. Dichloromethane is notable for its heavier density compared to water, aromatic odor, and excellent solubility in ethanol and diethyl ether, though it is somewhat insoluble in water. It dissolves a vast array of organic compounds.
Other Information on Dichloromethane
1. Synthesis of Dichloromethane
Dichloromethane is industrially produced through a radical reaction between methane or methyl chloride and chlorine gas at 400-500°C. This process yields a mixture including chloromethane, dichloromethane, trichloromethane (chloroform), and tetrachloromethane (carbon tetrachloride), from which DCM can be purified by distillation.
2. Purification of Dichloromethane
For organic synthesis, dehydration with a molecular sieve generally suffices. For precision work, distillation with calcium hydride as a drying agent is recommended, avoiding sodium to prevent explosive reactions.
3. How to Store Dichloromethane
Though stable, highly purified dichloromethane can decompose oxidatively when exposed to oxygen or light, producing harmful byproducts like hydrogen chloride or phosgene. To minimize this risk, stabilizers such as alcohols, olefins, and amines are added, and the substance should be stored in tightly sealed, light-protected containers.