Dichloromethane
| Dichloromethane | |
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Dichloromethane |
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Other names
Methylene chloride, methylene dichloride, Solmethine, Narkotil, Solaesthin, Di-clo, Freon 30, R-30, DCM, UN 1593, MDC |
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| Identifiers | |
| CAS number | 75-09-2  |
| PubChem | 6344 |
| ChemSpider | 6104 |
| UNII | 588X2YUY0A |
| EC number | 200-838-9 |
| KEGG | D02330 |
| ChEBI | CHEBI:15767 |
| ChEMBL | CHEMBL45967 |
| RTECS number | PA8050000 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | CH2Cl2 |
| Molar mass | 84.93 g/mol |
| Appearance | Colorless liquid |
| Density | 1.33 g/cm3, liquid |
| Melting point |
-96.7 °C, 176 K, -142 °F |
| Boiling point |
39.6 °C, 313 K, 103 °F |
| Solubility in water | 13 g/L at 20 °C |
| Vapor pressure | 47 kPa at 20 °C |
| Hazards | |
| MSDS | External MSDS |
| R-phrases | R40 |
| S-phrases | S23 S24/25 S36/37 |
| Main hazards | Harmful (Xn), Carc. Cat. 2B |
| NFPA 704 |
 1
2
0
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| Flash point | None |
| Autoignition temperature |
556 °C |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Dichloromethane (DCM)—or methylene chloride—is an 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 miscible with many organic solvents.[1]
Contents |
History [edit]
DCM was first prepared in 1840 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.
Production [edit]
DCM is produced by treating either methyl chloride or methane with chlorine gas at 400–500 °C. At these temperatures, both methane and methyl chloride undergo a series of reactions producing progressively more chlorinated products.[1]
- 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 methyl chloride, dichloromethane, chloroform, and carbon tetrachloride. These compounds are separated by distillation.
Uses [edit]
DCM's volatility and ability to dissolve a wide range of organic compounds makes it a useful solvent for many chemical processes. Concerns about its health effects have led to a search for alternatives in many of these applications.[1]
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.[2] Its volatility has led to its use as an aerosol spray propellant and as a blowing agent for polyurethane foams.
Specialized uses [edit]
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."
It is used in the garment printing industry for removal of heat-sealed garment transfers, and its volatility is exploited in novelty items: bubble lights and jukebox displays.
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.[3]
Toxicity [edit]
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.[4][5] DCM is also metabolized by the body to carbon monoxide potentially leading to carbon monoxide poisoning.[6] Acute exposure by inhalation has resulted in optic neuropathy[7] and hepatitis.[8] Prolonged skin contact can result in DCM dissolving some of the fatty tissues in skin, resulting in skin irritation or chemical burns.[9]
It may be carcinogenic, as it has been linked to cancer of the lungs, liver, and pancreas in laboratory animals.[10] DCM crosses the placenta. Fetal toxicity in women who are exposed to it during pregnancy, however, has not been proven.[11] In animal experiments, it was fetotoxic at doses that were maternally toxic but no teratogenic effects were seen.[10]
In many countries, products containing DCM must carry labels warning of its health risks.
In the European Union, the European Parliament voted in 2009 to ban the use of DCM in paint-strippers for consumers and many professionals.[12] The ban took effect in December 2010.[13]
In Europe, the Scientific Committee on Occupational Exposure Limits (SCOEL) recommends for DCM an occupational exposure limit (8h time-weighted average) of 100 ppm and a short-term exposure limit (15 min) of 200 ppm.[14]
In February 2013, the U.S. Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health warned that 14 bathtub refinishers have died since 2000 from DCM exposure.[15][16]
See also [edit]
References [edit]
- ^ a b c M. Rossberg et al. "Chlorinated Hydrocarbons" in Ullmann's Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a06_233.pub2
- ^ Office of Environmental Health Hazard Assessment (September 2000). "Dichloromethane". Public Health Goals for Chemicals in Drinking Water. California Environmental Protection Agency.
- ^ Shell Bitumen (2003-09-25). The Shell Bitumen Handbook. ISBN 978-0-7277-3220-0.
- ^ Rioux JP, Myers RA (1988). "Methylene chloride poisoning: a paradigmatic review". J Emerg Med 6 (3): 227–238. doi:10.1016/0736-4679(88)90330-7. PMID 3049777.
- ^ CDC (2012). "Fatal Exposure to Methylene Chloride Among Bathtub Refinishers — United States, 2000–2011". MMWR 61 (07): 119–122.
- ^ Fagin J, Bradley J, Williams D (1980). "Carbon monoxide poisoning secondary to inhaling methylene chloride". Br Med J 281 (6253): 1461. doi:10.1136/bmj.281.6253.1461. PMC 1714874. PMID 7437838.
- ^ Kobayashi A, Ando A, Tagami N, Kitagawa M, Kawai E, Akioka M, Arai E, Nakatani T, Nakano S, Matsui Y, Matsumura M (2008). "Severe optic neuropathy caused by dichloromethane inhalation". J Ocul Pharmacol and Ther 24 (6): 607–612. doi:10.1089/jop.2007.0100. PMID 19049266.
- ^ Cordes DH, Brown WD, Quinn KM (1988). "Chemically induced hepatitis after inhaling organic solvents". West J Med 148 (4): 458–460. PMC 1026148. PMID 3388849.
- ^ Wells G, Waldron H (1984). "Methylene chloride burns". Br J Ind Med 41 (3): 420. PMC 1009322. PMID 6743591.
- ^ a b USDHHS. "Toxicological Profile for Methylene Chloride" (PDF). Retrieved 2006-09-10.
- ^ Bell B, Franks P, Hildreth N, Melius J (1991). "Methylene chloride exposure and birthweight in Monroe County, New York". Environ Res 55 (1): 31–9. doi:10.1016/S0013-9351(05)80138-0. PMID 1855488.
- ^ "Dichloromethane to be banned in paint-strippers". 2009-01-14. Retrieved 2009-01-15.
- ^ "COMMISSION REGULATION (EU) No 276/2010 (Official Journal of the European Union, L 86/7)". 2010-04-01. Retrieved 2012-02-07.
- ^ "SCOEL recommendations". 2011-04-22. Retrieved 2011-04-22.
- ^ OSHA QuickTakes, February 1, 2013;
- ^ Methylene Chloride Hazards for Bathtub Refinishers
External links [edit]
- Fatal Exposure to Methylene Chloride Among Bathtub Refinishers
- International Chemical Safety Card 0058
- NIOSH Pocket Guide to Chemical Hazards 0414
- 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
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