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| Names | |||
|---|---|---|---|
| Preferred IUPAC name Chloromethane[2] | |||
| Other names | |||
| Identifiers | |||
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3D model (JSmol) | |||
| 1696839 | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider |
| ||
| ECHA InfoCard | 100.000.744 | ||
| EC Number |
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| 24898 | |||
| KEGG |
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| MeSH | Methyl+Chloride | ||
| RTECS number |
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| UNII | |||
| UN number | 1063 | ||
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| Properties | |||
| CH3Cl | |||
| Molar mass | 50.49 g·mol−1 | ||
| Appearance | Colorless gas | ||
| Odor | Faint, sweet odor[3] | ||
| Density | 1.003 g/mL (-23.8 °C, liquid)[1] 2.3065 g/L (0 °C, gas)[1] | ||
| Melting point | −97.4 °C (−143.3 °F; 175.8 K)[1] | ||
| Boiling point | −23.8 °C (−10.8 °F; 249.3 K)[1] | ||
| 5.325 g/L | |||
| logP | 1.113 | ||
| Vapor pressure | 506.09 kPa (at 20 °C (68 °F)) | ||
Henry's law constant (kH) | 940 nmol/(Pa⋅kg) | ||
| −32.0·10−6 cm3/mol | |||
| Structure | |||
| Tetragonal | |||
| Tetrahedron | |||
| 1.9 D | |||
| Thermochemistry | |||
Std molar entropy(S⦵298) | 234.36 J/(K⋅mol) | ||
Std enthalpy of formation(ΔfH⦵298) | −83.68 kJ/mol | ||
Std enthalpy of combustion(ΔcH⦵298) | −764.5–−763.5 kJ/mol | ||
| Hazards | |||
| GHS labelling: | |||
  | |||
| Danger | |||
| H221,H280,H351,H361fd,H373,H420 | |||
| P210,P260,P308+P313,P410+P403,P502 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | −20 °C (−4 °F; 253 K)[1] | ||
| 625 °C (1,157 °F; 898 K)[1] | |||
| Explosive limits | 8.1–17.4%[3] | ||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose) | 150–180 mg/kg (oral, rat)[1] 5.3 mg/L (4 h, inhalation, rat)[1] | ||
LC50 (median concentration) | 72,000 ppm (rat, 30 min) 2200 ppm (mouse, 6 h) 2760 ppm (mammal, 4 h) 2524 ppm (rat, 4 h)[4] | ||
LCLo (lowest published) | 20,000 ppm (guinea pig, 2 h) 14,661 ppm (dog, 6 h)[4] | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible) | TWA 100 ppm C 200 ppm 300 ppm (5-minute maximum peak in any 3 hours)[3] | ||
REL (Recommended) | Ca[3] | ||
IDLH (Immediate danger) | Ca [2000 ppm][3] | ||
| Related compounds | |||
Related alkanes | |||
Related compounds | 2-Chloroethanol | ||
| Supplementary data page | |||
| Chloromethane (data page) | |||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Chloromethane, also calledmethyl chloride,Refrigerant-40,R-40 orHCC 40, is anorganic compound with the chemical formulaCH3Cl. One of thehaloalkanes, it is a colorless, sweet-smelling, flammable gas. Methyl chloride is a crucialreagent in industrial chemistry, although it is rarely present in consumer products,[5] and was formerly utilized as arefrigerant. Most chloromethane isbiogenic.
Chloromethane is an abundantorganohalogen, anthropogenic or natural, in the atmosphere. Natural sources produce an estimated 4,100,000,000 kg/yr.[6]
Laboratory cultures of marinephytoplankton (Phaeodactylum tricornutum,Phaeocystis sp.,Thalassiosira weissflogii,Chaetoceros calcitrans,Isochrysis sp.,Porphyridium sp.,Synechococcus sp.,Tetraselmis sp.,Prorocentrum sp., andEmiliana huxleyi) produce CH3Cl, but in relatively insignificant amounts.[7][8] An extensive study of 30 species of polar macroalgae revealed the release of significant amounts of CH3Cl in onlyGigartina skottsbergii andGymnogongrus antarcticus.[9]
Thesalt marsh plantBatis maritima contains the enzymemethyl chloride transferase that catalyzes the synthesis of CH3Cl from S-adenosine-L-methionine and chloride.[10] This protein has been purified and expressed inE. 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.[10][11]
In the sugarcane industry, the organic waste is usually burned in the powercogeneration process. When contaminated by chloride, this waste burns, releasing methyl chloride in the atmosphere.[12]
Chloromethane has been detected in the low-mass Class 0 protostellar binary,IRAS 16293–2422, using theAtacama Large Millimeter Array (ALMA). It was also detected in the comet67P/Churyumov–Gerasimenko (67P/C-G) using the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument on theRosetta spacecraft.[13] The detections reveal that chloromethane can be formed instar-forming regions before planets or life is formed.[citation needed]
Chloromethane (originally called "chlorohydrate ofmethylene") was among the earliestorganochlorine compounds to be discovered when it was synthesized by French chemistsJean-Baptiste Dumas andEugène-Melchior Péligot in 1835 by boiling a mixture ofmethanol,sulfuric acid, andsodium chloride.[15] This method is the forerunner for that used today, which useshydrogen chloride instead of sulfuric acid and sodium chloride.[16]
Chloromethane is produced commercially by treatingmethanol withhydrochloric acid or hydrogen chloride, according to thechemical equation:[5]
A smaller amount of chloromethane is produced by treating a mixture ofmethane withchlorine at elevated temperatures. This method, however, also produces more highly chlorinated compounds such asdichloromethane,chloroform, andcarbon tetrachloride. For this reason, methane chlorination is usually only practiced when these other products are also desired. This chlorination method also cogenerates hydrogen chloride, which poses a disposal problem.[5]
Most of the methyl chloride present in the environment ends up being released to theatmosphere. After being released into the air, the atmospheric lifetime of this substance is about 10 months with multiple natural sinks, such as ocean, transport to the stratosphere, soil, etc.[17][18][19]
On the other hand, when the methyl chloride emitted is released to water, it will be rapidly lost byvolatilization. Thehalf-life of this substance in terms of volatilization in the river, lagoon and lake is 2.1 h, 25 h and 18 days, respectively.[20][21]
The amount of methyl chloride in thestratosphere is estimated to be 2×106 tonnes per year, representing 20–25% of the total amount of chlorine that is emitted to the stratosphere annually.[22][23]
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Large scale use of chloromethane is for the production ofdimethyldichlorosilane and relatedorganosilicon compounds.[5] These compounds arise via thedirect process. The relevant reactions are (Me = CH3):
Dimethyldichlorosilane (Me2SiCl2) is of particular value as a precursor tosilicones, buttrimethylsilyl chloride (Me3SiCl) andmethyltrichlorosilane (MeSiCl3) are also valuable.Smaller quantities are used as a solvent in the manufacture ofbutyl rubber and inpetroleum refining.
Chloromethane is employed as amethylating and chlorinating agent, e.g. the production ofmethylcellulose. It is also used in a variety of other fields: as an extractant forgreases,oils, andresins, as apropellant andblowing agent inpolystyrene foam production, as alocal anesthetic, as an intermediate in drug manufacturing, as acatalyst carrier in low-temperaturepolymerization, as a fluid for thermometric and thermostatic equipment, and as aherbicide.
Chloromethane was widely used as arefrigerant during the 1920s and 1930s, before being replaced by safer alternatives such aschlorofluorocarbons andhydrofluorocarbons. In the late 1920s, some manufacturers promoted chloromethane as a safer and less odorous option compared tosulfur dioxide andammonia.[24][25][26] However, a series of fatal leaks in 1928 and 1929 raised serious concerns related to its toxicity and flammability. Although chloromethane has a faint sweet odor, its subtle scent made leaks difficult to detect. To address this issue,acrolein was later added as a nasal-irritating tracer, enhancing leak detection and serving as a warning mechanism.[24][25]
Chloromethane was also once used for producing the lead-based gasoline additivestetramethyllead andtetraethyllead.[27][28][29]
During the late 1880s, chloromethane began to be employed in a limited extent for its anesthetic properties, serving as both a general and local agent.[29] Its use extended into the late 1920s as a component of the inhalation anesthetic Somnoform.[30][31]
Inhalation of chloromethane gas producescentral nervous system effects similar toalcohol intoxication. TheTLV is 50 ppm and theMAC is the same. Prolonged exposure may have mutagenic effects.[5]
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