Dichloromethane


Dichloromethane
Dichloromethane
Identifiers
CAS number 75-09-2 YesY
PubChem 6344
ChemSpider 6104 YesY
UNII 588X2YUY0A YesY
EC number 200-838-9
KEGG D02330 YesY
ChEBI CHEBI:15767 YesY
ChEMBL CHEMBL45967 YesY
RTECS number PA8050000
Jmol-3D images Image 1
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
NFPA 704.svg
1
2
0
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
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references
Near IR absorption spectrum of dichloromethane showing complicated overlapping overtones of mid IR absorption features.

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] 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.

Contents

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 + Cl2CH3Cl + HCl
CH3Cl + Cl2 → CH2Cl2 + HCl
CH2Cl2 + Cl2CHCl3 + HCl
CHCl3 + Cl2CCl4 + HCl

The output of these processes is a mixture of methyl chloride, dichloromethane, chloroform, and carbon tetrachloride. These compounds are separated by distillation.

Uses

Dichloromethane'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

The chemical compound's low boiling point allows the chemical to function as a heat engine that can extract movement from low grade temperatures. An example of a Dichloromethane heat engine is the drinking bird. The toy works at room temperature.

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 by model building hobbyists for joining plastic components together — it is commonly referred to as "Di-clo."

It is also 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.

Dichloromethane is used within 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

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 metabolized 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, the European Parliament voted in 2009 to ban the use of dichloromethane in paint-strippers for consumers and many professionals.[11] The ban took effect in December 2010.[citation needed]

In Europe, the Scientific Committee on Occupational Exposure Limits (SCOEL) recommends for dichloromethane an occupational exposure limit (8h time-weighted average) of 100 ppm and a short-term exposure limit (15 min) of 200 ppm. [12]

See also

References

  1. ^ 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
  2. ^ 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. 
  3. ^ Shell Bitumen (2003-09-25). The Shell Bitumen Handbook. ISBN 9780727732200. http://books.google.com/?id=bA1tIkRJL8kC&pg=PA277&lpg=PA277&dq=aliquot+bitumen+solvent+methylene+chloride. 
  4. ^ 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. 
  5. ^ 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. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1714874. 
  6. ^ 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. 
  7. ^ 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. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1026148. 
  8. ^ Wells G, Waldron H (1984). "Methylene chloride burns". Br J Ind Med 41 (3): 420. PMC 1009322. PMID 6743591. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1009322. 
  9. ^ a b USDHHS. "Toxicological Profile for Methylene Chloride" (PDF). http://www.atsdr.cdc.gov/toxprofiles/tp14.pdf. Retrieved 2006-09-10. 
  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. 
  11. ^ "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 2009-01-15. 
  12. ^ "SCOEL recommendations". 2011-04-22. http://ec.europa.eu/social/keyDocuments.jsp?type=0&policyArea=82&subCategory=153&country=0&year=0&advSearchKey=recommendation&mode=advancedSubmit&langId=en. Retrieved 2011-04-22. 

External links


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