Methylene dichloride (DCM, or methylene chloride, or dichloromethane) is a geminal organic compound with the formula CH2Cl2. This colorless, volatile liquid with a moderately sweet aroma is widely used as a solvent. Although it is not miscible with water, it is polar, and miscible with many organic solvents.
Methylene Dichloride; Dichloromethane
Methylene chloride, methylene dichloride, Solmethine, Narkotil, Solaesthin, Di-clo, Refrigerant-30 Freon-30, R-30, DCM, UN 1593, MDC
3D model (JSmol)
|Molar mass||84.93 g·mol−1|
|Density||1.3266 g/cm3 (20 °C)|
|Melting point||−96.7 °C (−142.1 °F; 176.5 K)|
|Boiling point|| 39.6 °C (103.3 °F; 312.8 K) |
decomposes at 720 °C
39.75 °C (103.55 °F; 312.90 K)
at 760 mmHg
|25.6 g/L (15 °C)|
17.5 g/L (25 °C)
15.8 g/L (30 °C)
5.2 g/L (60 °C)
|Solubility||Miscible in ethyl acetate, alcohol, hexanes, benzene, CCl4, diethyl ether, CHCl3|
|Vapor pressure||0.13 kPa (−70.5 °C)|
2 kPa (−40 °C)
19.3 kPa (0 °C)
57.3 kPa (25 °C)
79.99 kPa (35 °C)
Refractive index (nD)
|1.4244 (20 °C)|
|Viscosity||0.43 cP (20 °C)|
0.413 cP (25 °C)
Heat capacity (C)
Std enthalpy of
Std enthalpy of
|Safety data sheet||See: data page|
|GHS signal word||Warning|
|H315, H319, H335, H336, H351, H373|
|P261, P281, P305+351+338|
|Flash point||None, but can form flammable vapour-air mixtures above ~100 °C |
|556 °C (1,033 °F; 829 K)|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|1.25 g/kg (rats, oral)|
2 g/kg (rabbits, oral)
LC50 (median concentration)
|24,929 ppm (rat, 30 min)|
14,400 ppm (mouse, 7 hr)
LCLo (lowest published)
|5000 ppm (guinea pig, 2 hr)|
10,000 ppm (rabbit, 7 hr)
12,295 ppm (cat, 4.5 hr)
14,108 ppm (dog, 7 hr)
|US health exposure limits (NIOSH):|
|25 ppm over 8 hours (time weighted average), 125 ppm over 15 minutes (STEL)|
IDLH (Immediate danger)
|Ca [2300 ppm]|
|Supplementary data page|
|Refractive index (n),|
Dielectric constant (εr), etc.
|UV, IR, NMR, MS|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Natural sources of dichloromethane include oceanic sources, macroalgae, wetlands, and volcanoes. However, the majority of dichloromethane in the environment is the result of industrial emissions.
DCM is produced by treating either chloromethane or methane with chlorine gas at 400–500 °C. At these temperatures, both methane and chloromethane undergo a series of reactions producing progressively more chlorinated products. In this way, an estimated 400,000 tons were produced in the US, Europe, and Japan in 1993.
- CH4 + Cl2 → CH3Cl + HCl
- CH3Cl + Cl2 → CH2Cl2 + HCl
- CH2Cl2 + Cl2 → CHCl3 + HCl
- CHCl3 + Cl2 → CCl4 + HCl
DCM's volatility and ability to dissolve a wide range of organic compounds makes it a useful solvent for many chemical processes.. Carbon diselenide is produced by reacting selenium powder with dichloromethane vapor near 550°C.
- 2 Se + CH2Cl2 → CSe2 + 2 HCl
It is widely used as a paint stripper and a degreaser. In the food industry, it has been used to decaffeinate coffee and tea as well as to prepare extracts of hops and other flavorings. Its volatility has led to its use as an aerosol spray propellant and as a blowing agent for polyurethane foams.
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. An example of a DCM heat engine is the drinking bird. The toy works at room temperature.
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."
DCM is used in the material testing field of civil engineering; specifically it is used during the testing of bituminous materials as a solvent to separate the binder from the aggregate of an asphalt or macadam to allow the testing of the materials.
DCM is the least toxic of the simple chlorohydrocarbons, but it is not without health risks, as its high volatility makes it an acute inhalation hazard. It can also be absorbed through the skin.
Symptoms of acute overexposure to dichloromethane via inhalation include difficulty concentrating, dizziness, fatigue, nausea, headaches, numbness, weakness, and irritation of the upper respiratory tract and eyes. More severe consequences can include suffocation, loss of consciousness, coma, and death.
DCM is also metabolized by the body to carbon monoxide potentially leading to carbon monoxide poisoning. Acute exposure by inhalation has resulted in optic neuropathy and hepatitis. Prolonged skin contact can result in DCM dissolving some of the fatty tissues in skin, resulting in skin irritation or chemical burns.
It may be carcinogenic, as it has been linked to cancer of the lungs, liver, and pancreas in laboratory animals. Other animal studies showed breast cancer and salivary gland cancer. Research is not yet clear as to what levels may be carcinogenic. DCM crosses the placenta. Fetal toxicity in women who are exposed to it during pregnancy, however, has not been proven. In animal experiments, it was fetotoxic at doses that were maternally toxic but no teratogenic effects were seen.
In people with pre-existing heart problems, exposure to DCM can cause abnormal heart rhythms and/or heart attacks, sometimes without any other symptoms of overexposure. People with existing liver, nervous system, or skin problems may worsen after exposure to methylene chloride.
In many countries, products containing DCM must carry labels warning of its health risks.
In February 2013, the U.S. Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health warned that at least 14 bathtub refinishers have died since 2000 from DCM exposure. These workers had been working alone, in poorly ventilated bathrooms, with inadequate or no respiratory protection, and no training about the hazards of DCM. OSHA has since then issued a DCM standard. In the European Union, the European Parliament voted in 2009 to ban the use of DCM in paint-strippers for consumers and many professionals. The ban took effect in December 2010.
In Europe, the Scientific Committee on Occupational Exposure Limit Values (SCOEL) recommends for DCM an occupational exposure limit (8 h time-weighted average) of 100 ppm and a short-term exposure limit (15 min) of 200 ppm.
Dichloromethane is not classified as an ozone-depleting substance by the Montreal Protocol. The U.S. Clean Air Act does not regulate dichloromethane as an ozone depleter. According to the EPA, the atmospheric lifetime of dichloromethane is very short, such that the substance decomposes before reaching the ozone layer.
Ozone concentrations measured at the midlatitudes from the ground up through the stratosphere from 1998 to 2016 have declined by 2.2 Dobson units. The reasons for this decline are unclear, but one unverified hypothesis is the presence of short-lived substances such as dichloromethane in the lower atmosphere.
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Reprinted in German in:
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|Wikimedia Commons has media related to Dichloromethane.|
- International Chemical Safety Card 0058
- "NIOSH Pocket Guide to Chemical Hazards #0414". National Institute for Occupational Safety and Health (NIOSH).
- National Pollutant Inventory – Dichloromethane Fact Sheet
- Dichloromethane at National Toxicology Program
- IARC Summaries & Evaluations Vol. 71 (1999)
- Canadian Environmental Protection Act Priority Substances List Assessment Report
- Organic Compounds Database
- Sustainable uses and Industry recommendations