Dichloromethane: Properties and Applications

What are the key physical and chemical properties of dichloromethane?

Dichloromethane (DCM), also known as methylene chloride, is a colourless, volatile liquid with a sweet, chloroform-like odour. It has a boiling point of 39.6 °C and a density of 1.33 g/cm³ at 20 °C. It is immiscible with water but miscible with most organic solvents, including ethanol, ether, and benzene. Its low polarity and high solvating power make it ideal for extracting organic compounds from aqueous solutions. DCM is stable under normal conditions but can decompose under strong UV light or high temperatures, releasing toxic phosgene (carbonyl chloride).

How is dichloromethane used in laboratory and industrial processes?

In laboratory settings, dichloromethane is commonly used for liquid-liquid extractions, chromatography, and as a solvent in organic synthesis. It is also employed in the pharmaceutical industry for drug purification and in the production of pesticides and adhesives. In the food industry, it is used in the decaffeination of coffee and tea, though its use is strictly regulated. Due to its toxicity and potential carcinogenicity, its use is increasingly restricted under regulations such as REACH and GHS. Safety measures include use in fume hoods and personal protective equipment.

What are the safety and regulatory considerations for dichloromethane?

Dichloromethane is classified as a hazardous substance under GHS and is listed in the EU’s REACH regulation. It is a suspected carcinogen (IARC Group 2B) and can cause acute toxicity via inhalation or skin absorption. Long-term exposure may lead to liver and kidney damage. Regulatory bodies such as the UK Health and Safety Executive (HSE) and the US EPA have imposed strict controls on its use. Alternatives like ethyl acetate or supercritical CO₂ are being adopted where feasible.

Related concepts

Dichloromethane is often compared with other halogenated solvents such as chloroform (trichloromethane) and carbon tetrachloride. Its use is monitored under ISO standards for chemical safety, and compliance with SDS and CoA documentation is essential in procurement and regulatory submissions.