Dichloromethane

From Wikipedia, the free encyclopedia

Dichloromethane
General
Systematic name	Dichloromethane
Other names	Methylene chloride DCM
Molecular formula	CH2Cl2
SMILES	C(Cl)Cl
Molar mass	84.93 g/mol
Appearance	Colorless liquid
CAS number	[75-09-2]
Properties
Density and phase	1.3255 g/cm³, liquid
Solubility in water	1.3 g/100 mL (20 °C)
other solvents	Infinitely miscible with most organic solvents
Melting point	−96.7 °C (175.7 K)
Boiling point	39.8 °C (312.8 K)
Vapor Pressure	6.83 psi @ 20ºC
Viscosity	0.44 cP at 20 °C
Hazards
MSDS	External MSDS
Main hazards	Harmful (Xn)
NFPA 704	1 2 0
Flash point	None
R/S statement	R: 40 S: 23/24/25/36/37
RTECS number	PA8050000
Supplementary data page
Structure and properties	n (1.424) εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Related Chloromethanes	Chloromethane Chloroform Carbon tetrachloride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Dichloromethane or methylene chloride is the chemical compound with the formula CH₂Cl₂. It is a colorless, volatile liquid with a moderately sweet aroma. It is widely used as a solvent, the general view being that it is one of the less harmful of the chlorocarbons.

Dichloromethane 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.

[edit] Production

Industrially, dichloromethane is produced by reacting 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.

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 ideal solvent for many chemical processes. It is widely used as a paint stripper and a degreaser. In the food industry, it is used to decaffeinate coffee and to prepare extracts of hops and other flavorings. It is used to chemically weld certain plastics (for example, it is used to seal the casing of electric meters). Its volatility has led to its use as an aerosol spray propellant and as a blowing agent for polyurethane foams. It is also used as a fumigant pesticide for stored strawberries and grains. It is also the most common "active" component in Drinking Birds. Concerns about its health effects have led to a search for alternatives in many of these applications.

Near IR absorption spectrum of dichloromethane showing complicated overlapping overtones of mid IR absorption features.

It is used in Christmas lights called bubble lights, in a sealed vial which bubbles when the incandescent light bulb below it is lit. Wurlitzer also used it in their 1940's "bubbler" style jukeboxes. The bubble tubes were up to 30 inches long and used resistors to provide the heat to boil the liquid in a small constricted chamber that had bits of rock and a special glass valve to concentrate the small bubbles into larger ones. It is still used today in their reproduction machines. Dichloromethane is quite often used as a farming tool in Eastern and Central America as a gene adaptation tool.^{[citation needed]}

[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. Dichloromethane is also metabolised by the body to carbon monoxide potentially leading to carbon monoxide poisoning.^[1] Prolonged skin contact can result in the dichloromethane dissolving some of the fatty tissues in skin, resulting in skin irritation or chemical burns.^[2]

It may be carcinogenic, as it has been linked to cancer of the lungs, liver, and pancreas in laboratory animals.^[3] Dichloromethane is a mutagen/teratogen and crosses the placenta, causing fetal toxicity in women who are exposed to it during pregnancy.^[4] In animal experiments it was fetotoxic at doses that were maternally toxic but no teratogenic effects were seen.^[3]

In many countries products containing dichloromethane must carry labels warning of its health risks.

[edit] Footnotes

[edit] External links

• National Pollutant Inventory - Dichloromethane Fact Sheet

• Links to external chemical sources