Dichloromethane

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Dichloromethane
Dichloromethane.svg Dichloromethane-3D-vdW.png
Sample of dichloromethane.jpg
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 (−142.1 °F; 176.5 K)
Boiling point 39.6 °C (103.3 °F; 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
Main hazards Harmful (Xn), Carc. Cat. 2B
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
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 (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
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] One of the most well-known applications of dichloromethane is in the drinking bird heat engine.

Occurrence[edit]

Natural sources of dichloromethane include oceanic sources, macroalgae, wetlands, and volcanoes.[2] However, the majority of dichloromethane in the environment is the result of industrial emissions..[2]

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 + 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.

DCM was first prepared in 1839 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.[3]

Uses[edit]

DCM's volatility and ability to dissolve a wide range of organic compounds makes it a useful solvent for many chemical processes.[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.[4] 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.[5]

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.[6][7]

DCM is also metabolized by the body to carbon monoxide potentially leading to carbon monoxide poisoning.[8] Acute exposure by inhalation has resulted in optic neuropathy[9] and hepatitis.[10] Prolonged skin contact can result in DCM dissolving some of the fatty tissues in skin, resulting in skin irritation or chemical burns.[11]

It may be carcinogenic, as it has been linked to cancer of the lungs, liver, and pancreas in laboratory animals.[12] DCM crosses the placenta. Fetal toxicity in women who are exposed to it during pregnancy, however, has not been proven.[13] In animal experiments, it was fetotoxic at doses that were maternally toxic but no teratogenic effects were seen.[12]

Regulation[edit]

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.[14][15][16] OSHA has since then issued a DCM standard.[17] The Massachusetts Department of Public Health posted a similar warning in April 2012.[18]

In the European Union, the European Parliament voted in 2009 to ban the use of DCM in paint-strippers for consumers and many professionals.[19] The ban took effect in December 2010.[20]

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.[21]

Concerns about its health effects have led to a search for alternatives in many of these applications.[1][22]

See also[edit]

References[edit]

  1. ^ a b c d 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. ^ a b Gordon W. Gribble (2009). Naturally Occurring Organohalogen Compounds. Springer. 
  3. ^ V. Regnault (1839) "De l'action du chlore sur les éthers hydrochloriques de l'alcool et de l'esprit de bois, et de plusieurs points de la théorie des éthers" (On the action of chlorine on the hydrochloric ethers of ethanol and methanol, and on several points of the theory of ethers), Annales de chimie et physique, series 2, 71 : 353-431; see especially: "Seconde partie. De l'action du chlore sur l'éther hydrochlorique de l'esprit de bois" (Second part. On the action of chlorine on the hydrochloric ether of methanol [i.e., chloromethane]), pages 377-380. Regnault gives dichloromethane the name éther hydrochlorique monochloruré (monochlorinated hydrochloric ether). Note: Regnault gives the empirical formula for dichloromethane as C2H4Cl4 because during that era, chemists used incorrect atomic masses.
    Reprinted in German in:
  4. ^ Office of Environmental Health Hazard Assessment (September 2000). "Dichloromethane". Public Health Goals for Chemicals in Drinking Water. California Environmental Protection Agency. 
  5. ^ Shell Bitumen (2003-09-25). The Shell Bitumen Handbook. ISBN 978-0-7277-3220-0. 
  6. ^ 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. 
  7. ^ CDC (2012). "Fatal Exposure to Methylene Chloride Among Bathtub Refinishers — United States, 2000–2011". MMWR 61 (07): 119–122. 
  8. ^ 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. 
  9. ^ 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. 
  10. ^ 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. 
  11. ^ Wells G, Waldron H (1984). "Methylene chloride burns". Br J Ind Med 41 (3): 420. PMC 1009322. PMID 6743591. 
  12. ^ a b USDHHS. "Toxicological Profile for Methylene Chloride" (PDF). Retrieved 2006-09-10. 
  13. ^ 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. 
  14. ^ OSHA QuickTakes, February 1, 2013;
  15. ^ Methylene Chloride Hazards for Bathtub Refinishers, OSHA-NIOSH Hazard Alert
  16. ^ Dangers of Bathtub Refinishing, NIOSH Science Blog, Ronald M. Hall February 4, 2013
  17. ^ OSHA Standard for Methylene Chloride
  18. ^ Bathtub Refinisher Dies From Exposure to Methylene Chloride, FACE Facts Safety Alert, Occupational Health Surveillance Program, Massachusetts Department of Public Health, April 2012
  19. ^ "EU Banning Most DCM Paint Strippers," PaintSquare News, retrieved 1/5/14.
  20. ^ "COMMISSION REGULATION (EU) No 276/2010 (Official Journal of the European Union, L 86/7)". 2010-04-01. Retrieved 2012-02-07. 
  21. ^ "SCOEL recommendations". 2011-04-22. Retrieved 2011-04-22. 
  22. ^ Summary of Regulations Controlling Air Emissions from Paint Stripping and Miscellaneous Surface Coating Operations. U.S. Environmental Protection Agency - NESHAP 6H. 

External links[edit]