Chloromethane

Chloromethane
IUPAC name Chloromethane
Other names Artic Freon 40 R 40 Methyl chloride Monochloromethane
Identifiers
CAS number	74-87-3 Y
PubChem	6327
ChemSpider	6087 Y
UNII	A6R43525YO Y
EC number	200-817-4
UN number	1063
KEGG	C19446 N
MeSH	Methyl+Chloride
ChEBI	CHEBI:36014 Y
ChEMBL	CHEMBL117545 Y
RTECS number	PA6300000
Beilstein Reference	1696839
Gmelin Reference	24898
Jmol-3D images	Image 1
SMILES CCl
InChI InChI=1S/CH3Cl/c1-2/h1H3 Y Key: NEHMKBQYUWJMIP-UHFFFAOYSA-N Y
Properties
Molecular formula	CH3Cl
Molar mass	50.49 g mol−1
Appearance	Colorless gas
Density	1.003 g/mL (-23.8 °C, liquid)2.3065 g/L (0 °C, gas)
Melting point	−97.4 °C (−143.3 °F; 175.8 K)
Boiling point	−23.8 °C (−10.8 °F; 249.3 K)
Solubility in water	5.325 g L−1
log P	1.113
Vapor pressure	506.09 kPa (at 20.0 °C)
kH	940 nmol Pa−1 kg−1
Structure
Coordination geometry	Tetragonal
Molecular shape	Tetrahedron
Thermochemistry
Std molar entropy So298	234.36 J K−1 mol−1
Std enthalpy of formation ΔfHo298	−83.68 kJ mol−1
Std enthalpy of combustion ΔcHo298	−764.5–−763.5 kJ mol−1
Hazards
MSDS	External MSDS
GHS pictograms
GHS signal word	DANGER
GHS hazard statements	H220, H351, H373
GHS precautionary statements	P210, P281, P410+403
EU Index	602-001-00-7
EU classification	F+ Xn T
R-phrases	R12, R40, R48/20
S-phrases	(S2), S16, S33
NFPA 704	4 2 0
Flash point	−20 °C (−4 °F; 253 K)
Autoignition temperature	625 °C (1,157 °F; 898 K)
Explosive limits	7–19%
LD50	1800 mg/kg (oral, rat) 5.3 mg/L/4 h (inhalation, rat)
Related compounds
Related alkanes	Chloroiodomethane Bromochloromethane Dibromochloromethane
Related compounds	2-Chloroethanol
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)
N (verify) (what is: Y/N?)
Infobox references

Chloromethane, also called methyl chloride, R-40 or HCC 40, is a chemical compound of the group of organic compounds called haloalkanes. It was once widely used as a refrigerant. It is a colorless extremely flammable gas with a mildly sweet odor, which is, however, detected at possibly toxic levels. Due to concerns about its toxicity, it is no longer present in consumer products. Chloromethane was first synthesized by the French chemists Jean-Baptiste Dumas and Eugene Peligot in 1835 by boiling a mixture of methanol, sulfuric acid, and sodium chloride. This method is similar to that used today.

Occurrence

Chloromethane is the most abundant organohalogen, anthropogenic or natural, in the atmosphere.

Marine

Laboratory cultures of marine phytoplankton (Phaeodactylum tricornutum, Phaeocystis sp., Thalassiosira weissflogii, Chaetoceros calcitrans, Isochrysis sp., Porphyridium sp., Synechococcus sp., Tetraselmis sp., Prorocentrum sp., and Emiliana huxleyi) produce CH₃Cl, but in relatively insignificant amounts. An extensive study of 30 species of polar macroalgae revealed the release of significant amounts of CH₃Cl in only Gigartina skottsbergii and Gymnogongrus antarcticus.

Biogenesis

The salt marsh plant Batis maritima contains the enzyme methyl chloride transferase that catalyzes the synthesis of CH₃Cl from S-adenosine-L-methionine and chloride. This protein has been purified and expressed in E. coli, and seems to be present in other organisms such as white rot fungi (Phellinus pomaceus), red algae (Endocladia muricata), and the ice plant (Mesembryanthemum crystallinum), each of which is a known CH₃Cl producer.

Production

Large amounts of chloromethane are produced naturally in the oceans by the action of sunlight on biomass and chlorine in sea foam. However, all chloromethane that is used in industry is produced synthetically.

Most chloromethane is prepared by reacting methanol with hydrogen chloride, according to the chemical equation

CH₃OH + HCl → CH₃Cl + H₂O

This can be carried out either by bubbling hydrogen chloride gas through boiling methanol with or without a zinc chloride catalyst, or by passing combined methanol and hydrogen chloride vapors over an alumina catalyst at 350 °C.

A smaller amount of chloromethane is produced by heating a mixture of methane and chlorine to over 400 °C. However, this method also results in more highly chlorinated compounds such as methylene chloride and chloroform and is usually only used when these other products are also desired.

Further reaction of chloromethane with chlorine can produce dichloromethane, trichloromethane (known as chloroform) and tetrachloromethane (also known as carbon tetrachloride).

Uses

Chloromethane was a widely used refrigerant, but its use has been discontinued due to its toxicity and flammability. Chloromethane was also once used for producing lead-based gasoline additives (tetramethyllead).

The most important use of chloromethane today is as a chemical intermediate in the production of silicone polymers. Smaller quantities are used as a solvent in the manufacture of butyl rubber and in petroleum refining.

Chloromethane is employed as a methylating and chlorinating agent in organic chemistry. It is also used in a variety of other fields: as an extractant for greases oils and resins, as a propellant and blowing agent in polystyrene foam production, as a local anesthetic, as an intermediate in drug manufacturing, as a catalyst carrier in low-temperature polymerization, as a fluid for thermometric and thermostatic equipment, and as a herbicide.

Safety

Inhalation of chloromethane gas produces central nervous system effects similar to drug intoxication. Exposure may cause drowsiness, dizziness, or confusion and difficulty breathing, walking or speaking may occur. At higher concentrations, paralysis, seizures, and coma can result.

In case of ingestion, nausea and vomiting may occur. Skin contact, when in the form of a refrigerated liquid, may result in frostbite. Contact with the eyes may result in dim vision, and widely dilated pupils that react slowly to changes in light.

Chronic exposure to chloromethane has been linked to birth defects in mice. In humans, exposure to chloromethane during pregnancy may cause the fetus' lower spinal column, pelvis, and legs to form incorrectly, but this has not been conclusively demonstrated.

In 1997, a re-investigation of Boston's Cocoanut Grove nightclub fire in 1942 cited a chloromethane leak from a refrigerator as a major cause of that disaster.

External links

• International Chemical Safety Card 0419
• NIOSH Pocket Guide to Chemical Hazards 0403
• Data sheet at inchem.org
• Toxicological information
• Information about chloromethane
• Concise International Chemical Assessment Document 28 on chloromethane
• IARC Summaries & Evaluations Vol. 71 (1999)