Dichloromethane
From Wikipedia, the free encyclopedia
| Dichloromethane | |
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| IUPAC name |
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| Other names | Methylene chloride, methylene dichloride, Solmethine, Narkotil, Solaesthin, Di-clo, Freon 30, R-30, DCM, UN 1593, MDC |
| Identifiers | |
| CAS number | [] |
| PubChem | |
| EC number | |
| KEGG | |
| ChEBI | |
| RTECS number | PA8050000 |
| SMILES |
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| InChI |
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| Properties | |
| Molecular formula | CH2Cl2 |
| Molar mass | 84.93 g/mol |
| Appearance | Colorless liquid |
| Density | 1.3266 g/cm³, liquid |
| Melting point |
-96.7 °C (175.7 K) |
| Boiling point |
40 °C (312.8 K) |
| 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 |
| NFPA 704 |
 1
2
0
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| Flash point | None |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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Dichloromethane (DCM or methylene chloride) is the organic compound with the formula CH2Cl2. This colorless, volatile liquid with a moderately sweet aroma is widely used as a solvent. More than 500,000 tons were produced in 1991. Although it is not miscible with water, it is miscible with many organic solvents.[1] It was first prepared in 1840 by the French chemist Henri Victor Regnault, who isolated it from a mixture of chloromethane and chlorine that had been exposed to sunlight.
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[edit] Production
Dichloromethane 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.
[edit] Uses
Dichloromethane's volatility and ability to dissolve a wide range of organic compounds makes it an 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 is 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.
[edit] Specialized uses
Dichloromethane 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 in the model-making industry for joining plastic components together - it is commonly referred to as "Di-clo."
Also used in the garment printing industry for removal of heat-sealed garment transfers. Usually sold in cans with methanol as the propellant gas. Its volatility is exploited in novelty items - drinking birds, bubble lights, and jukebox displays.
Dichloromethane is used within the material testing field of civil engineering, specifically it it 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]
[edit] Toxicity
Dichloromethane is the least toxic of the simple chlorohydrocarbons, but it is not without its health risks as its high volatility makes it an acute inhalation hazard.[4] Dichloromethane is also metabolised by the body to carbon monoxide potentially leading to carbon monoxide poisoning.[5] Acute exposure by inhalation has resulted in optic neuropathy[6] and hepatitis.[7] Prolonged skin contact can result in the dichloromethane dissolving some of the fatty tissues in skin, resulting in skin irritation or chemical burns.[8]
It may be carcinogenic, as it has been linked to cancer of the lungs, liver, and pancreas in laboratory animals.[9] Dichloromethane crosses the placenta. Fetal toxicity in women who are exposed to it during pregnancy however has not been proven.[10] In animal experiments it was fetotoxic at doses that were maternally toxic but no teratogenic effects were seen.[9]
In many countries products containing dichloromethane must carry labels warning of its health risks.
In the European Union use of dichloromethane in paint-strippers was banned for consumers and many professionals.[11]
[edit] References
- ^ 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. http://www.oehha.ca.gov/water/phg/pdf/dcm.pdf.
- ^ Shell Bitumen. "The Shell Bitumen Handbook". http://books.google.co.uk/books?id=bA1tIkRJL8kC&pg=PA277&lpg=PA277&dq=aliquot+bitumen+solvent+methylene+chloride&source=bl&ots=paPjPrz_YQ&sig=OxFZ3GvgkLfRVnabn6qR8_dqHNo&hl=en&ei=F0nKSdz4EOHKjAeAzOTNAw&sa=X&oi=book_result&resnum=1&ct=result.
- ^ Rioux JP, Myers RA (1988). "Methylene chloride poisoning: a paradigmatic review". J Emerg Med 6 (3): 227–238. doi:. PMID 3049777.
- ^ Fagin J, Bradley J, Williams D (1980). "Carbon monoxide poisoning secondary to inhaling methylene chloride". Br Med J 281 (6253): 1461. doi:. 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:. PMID 19049266.
- ^ Cordes DH, Brown WD, Quinn KM (1988). "Chemically induced hepatitis after inhaling organic solvents". West J Med 148 (4): 458–460. PMID 3388849.
- ^ Wells G, Waldron H (1984). "Methylene chloride burns". Br J Ind Med 41 (3): 420. PMID 6743591.
- ^ a b USDHHS. "Toxicological Profile for Methylene Chloride" (PDF). http://www.atsdr.cdc.gov/toxprofiles/tp14.pdf. Retrieved on 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:. PMID 1855488.
- ^ "Dichloromethane to be banned in paint-strippers". 2009-01-14. http://www.europarl.europa.eu/news/expert/infopress_page/064-46096-012-01-03-911-20090113IPR46095-12-01-2009-2009-false/default_en.htm. Retrieved on 2009-01-15.
[edit] External links
- International Chemical Safety Card 0058
- NIOSH Pocket Guide to Chemical Hazards 0414
- National Pollutant Inventory - Dichloromethane Fact Sheet
- MSDS at Oxford University
- Dichloromethane at National Toxicology Program
- IARC Summaries & Evaluations Vol. 71 (1999)
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