Chloromethane
| Chloromethane | |
|---|---|
| Chloromethane | |
| Other names Monochloromethane, Methyl chloride, Artic, Freon 40, R 40, UN 1063 | |
| style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers | |
| CAS number | 74-87-3 
|
| PubChem | 6327 |
| ChemSpider | 6087 |
| EC number | 200-817-4 |
| ChEBI | 36014 |
| RTECS number | PA6300000 |
| SMILES | Script error: No such module "collapsible list". |
| InChI | Script error: No such module "collapsible list". |
| InChI key | NEHMKBQYUWJMIP-UHFFFAOYAW |
| style="background: #F8EABA; text-align: center;" colspan="2" | Properties | |
| Molecular formula | CH3Cl |
| Molar mass | 50.49 g/mol |
| Appearance | Colorless gas with a faint sweet odor |
| Density | 2.22 kg/m3 (0 °C) |
| Melting point |
−97.7 °C (176 K) (-143.9 °F) |
| Boiling point |
-24.2 °C (249 K) (-11.6 °F) |
| Solubility in water | 5.325 g/l (25 °C) |
| log P | 0.91 |
| Vapor pressure | 490 kPa (20 °C) ; 71 PSI (68°F) |
| style="background: #F8EABA; text-align: center;" colspan="2" | Structure | |
| Molecular shape | Tetrahedral |
| style="background: #F8EABA; text-align: center;" colspan="2" | Hazards | |
| EU classification | Extremely flammable (F+), Harmful (Xn), Carc. Cat. 3 |
| R-phrases | R10, R40, R48/20 |
| S-phrases | S9, S16, S33 |
| NFPA 704 | |
| Flash point | -46 °C |
| Autoignition temperature |
625 °C |
 (what is this?) (verify)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
| 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 minorly 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.
Contents
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 [1][2]. An extensive study of 30 species of polar macroalgae revealed the release of significant amounts of CH3Cl in only Gigartina skottsbergii and Gymnogongrus antarcticus[3].
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 [4]. 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 crystallium), each of which is a known CH3Cl producer [5][6].
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
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 hydrochloric acid 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. Victims may feel drowsy, dizzy, or confused and have difficulty breathing, with gasping and choking, walking or speaking. At higher concentrations, paralysis, seizures, and coma may result.
In case of ingestion nausea and vomiting may result. Skin contact when in the form of a refrigerated liquid may result in frostbite. Contact with eyes may result in dim vision, 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.
References
- ↑ Scarratt MG, Moore RM (1996) Production of Methyl Chloride and Methyl Bromide in Laboratory Cultures of Marine Phytoplankton. Mar Chem 54: 263
- ↑ Scarratt MG, Moore RM (1998) Production of Methyl Bromide and Methyl Chloride in Laboratory Cultures of Marine Phytoplankton II. Mar Chem 59: 311
- ↑ Laturnus F (2001) Marine Macroalgae in Polar Regions as Natural Sources for Volatile Organohalogens. Environ Sci Pollut Res 8: 103
- ↑ Ni X, Hager LP (1998) cDNA Cloning of Batis maritima Methyl Chloride Transferase and Purification of the Enzyme. Proc Natl Acad Sci USA 95: 12866
- ↑ Ni X, Hager LP (1998) cDNA Cloning of Batis maritima Methyl Chloride Transferase and Purification of the Enzyme. Proc Natl Acad Sci USA 95: 12866
- ↑ Ni X, Hager LP (1999) Expression of Batis maritima Methyl Chloride Transferase in Escherichia coli. Proc Natl Acad Sci USA 96: 3611
External links
- International Chemical Safety Card 0419
- NIOSH Pocket Guide to Chemical Hazards 0403
- MSDS at Oxford University
- Data sheet at inchem.org
- Toxicological information
- Information about chloromethane
- Concise International Chemical Assessment Document 28 on chloromethane
- IARC Summaries & Evaluations Vol. 71 (1999)
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