Chloromethane
Chloromethane, also called methyl chloride, Refrigerant-40, R-40 or HCC 40, is an organic compound with the chemical formula CH3Cl. One of the haloalkanes, it is a colorless, odorless, flammable gas. Methyl chloride is a crucial reagent in industrial chemistry, although it is rarely present in consumer products, [5] and was formerly utilized as a refrigerant.
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| Names | |||
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| Preferred IUPAC name Chloromethane[2] | |||
| Other names | |||
| Identifiers | |||
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3D model (JSmol) |
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| 1696839 | |||
| ChEBI |
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| ChEMBL |
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| ChemSpider |
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| ECHA InfoCard | 100.000.744 | ||
| EC Number |
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| 24898 | |||
| KEGG |
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| MeSH | Methyl+Chloride | ||
PubChem CID |
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| RTECS number |
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| UNII |
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| UN number | 1063 | ||
CompTox Dashboard (EPA) |
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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−1 | |||
| log P | 1.113 | ||
| Vapor pressure | 506.09 kPa (at 20 °C (68 °F)) | ||
Henry's law constant (kH) | 940 nmol Pa−1 kg−1 | ||
| -32.0·10−6 cm3/mol | |||
| Structure | |||
| Tetragonal | |||
| Tetrahedron | |||
| 1.9 D | |||
| Thermochemistry | |||
Std molar entropy (S⦵298) | 234.36 J K−1 mol−1 | ||
Std enthalpy of formation (ΔfH⦵298) | −83.68 kJ mol−1 | ||
Std enthalpy of combustion (ΔcH⦵298) | −764.5–−763.5 kJ mol−1 | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards | carcinogen | ||
| GHS labelling: | |||
| Danger | |||
| H220, H351, H373 | |||
| P210, P281, P410+P403 | |||
| 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 hr) 2760 ppm (mammal, 4 hr) 2524 ppm (rat, 4 hr)[4] | ||
LCLo (lowest published) | 20,000 ppm (guinea pig, 2 hr) 14,661 ppm (dog, 6 hr)[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 their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) | |||
Occurrence
Chloromethane is an abundant organohalogen, anthropogenic or natural, in the atmosphere.[6]
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.[7][8] An extensive study of 30 species of polar macroalgae revealed the release of significant amounts of CH3Cl in only Gigartina skottsbergii and Gymnogongrus antarcticus.[9]
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.[10] 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.[10][11]
Sugarcane and the emission of methyl chloride
In the sugarcane industry, the organic waste is usually burned in the power cogeneration process. When contaminated by chloride, this waste burns, releasing methyl chloride in the atmosphere.[12]
Interstellar detections
Chloromethane has been detected in the low-mass Class 0 protostellar binary, IRAS 16293–2422, using the Atacama Large Millimeter Array (ALMA). It was also detected in the comet 67P/Churyumov–Gerasimenko (67P/C-G) using the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument on the Rosetta spacecraft.[13] The detections reveal that chloromethane can be formed in star-forming regions before planets or life is formed.
Production
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 the forerunner for that used today but uses hydrogen chloride instead of sulfuric acid and sodium chloride.[15]
Chloromethane is produced commercially by treating methanol with hydrochloric acid or hydrogen chloride, according to the chemical equation:[5]
- CH3OH + HCl → CH3Cl + H2O
A smaller amount of chloromethane is produced by treating a mixture of methane with chlorine at elevated temperatures. This method, however, also produces more highly chlorinated compounds such as dichloromethane, chloroform, and carbon 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]
Dispersion in the environment
Most of the methyl chloride present in the environment ends up being released to the atmosphere. 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.[16][17][18]
On the other hand, when the methyl chloride emitted is released to water, it will be rapidly lost by volatilization. The [half-life] of this substance in terms of volatilization in the river, lagoon and lake is 2.1 h, 25 h and 18 days, respectively.[19][20]
The amount of methyl chloride in the stratosphere is estimated to be 2 x 106 tonnes per year, representing 20-25% of the total amount of chlorine that is emitted to the stratosphere annually.[21][22]
Uses
Large scale use of chloromethane is for the production of dimethyldichlorosilane and related organosilicon compounds.[5] These compounds arise via the direct process. The relevant reactions are (Me = CH3):
- x MeCl + Si → Me3SiCl, Me2SiCl2, MeSiCl3, Me4Si2Cl2, ...
Dimethyldichlorosilane (Me2SiCl2) is of particular value as a precursor to silicones, but trimethylsilyl chloride (Me3SiCl) and methyltrichlorosilane (MeSiCl3) are also valuable. 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, e.g. the production of methylcellulose. 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.
Obsolete applications
Chloromethane was a widely used refrigerant, but its use has been discontinued. Chloromethane was also once used for producing lead-based gasoline additives (tetramethyllead).
Safety
Inhalation of chloromethane gas produces central nervous system effects similar to alcohol intoxication. The TLV is 50 ppm and the MAC is the same. Prolonged exposure may have mutagenic effects.[5]
References
- ^ a b c d e f g h i j k Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health
- ^ International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 1033. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
- ^ a b c d e NIOSH Pocket Guide to Chemical Hazards. "#0403". National Institute for Occupational Safety and Health (NIOSH).
- ^ a b "Methyl chloride". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
- ^ a b c d e Rossberg, M.; Lendle, W.; Pfleiderer, G.; Tögel, A.; Dreher, E. L.; Langer, E.; Rassaerts, H.; Kleinschmidt, P.; Strack (2006). "Chlorinated Hydrocarbons". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a06_233.pub2.
- ^ Lim, Y.-K.; Phang, S.-M.; Rahman, N. Abdul; Sturges, W. T.; Malin, G. (2017). "REVIEW: Halocarbon Emissions from Marine Phytoplankton and Climate Change". Int. J. Environ. Sci. Technol.: 1355–1370. doi:10.1007/s13762-016-1219-5. S2CID 99300836.
- ^ Scarratt MG, Moore RM (1996). "Production of Methyl Chloride and Methyl Bromide in Laboratory Cultures of Marine Phytoplankton". Mar Chem. 54 (3–4): 263–272. doi:10.1016/0304-4203(96)00036-9.
- ^ Scarratt MG, Moore RM (1998). "Production of Methyl Bromide and Methyl Chloride in Laboratory Cultures of Marine Phytoplankton II". Mar Chem. 59 (3–4): 311–320. doi:10.1016/S0304-4203(97)00092-3.
- ^ Laturnus F (2001). "Marine Macroalgae in Polar Regions as Natural Sources for Volatile Organohalogens". Environ Sci Pollut Res. 8 (2): 103–108. doi:10.1007/BF02987302. PMID 11400635. S2CID 570389.
- ^ a b Ni X, Hager LP (1998). "cDNA Cloning of Batis maritima Methyl Chloride Transferase and Purification of the Enzyme". Proc Natl Acad Sci USA. 95 (22): 12866–71. Bibcode:1998PNAS...9512866N. doi:10.1073/pnas.95.22.12866. PMC 23635. PMID 9789006.
- ^ Ni X, Hager LP (1999). "Expression of Batis maritima Methyl Chloride Transferase in Escherichia coli". Proc Natl Acad Sci USA. 96 (7): 3611–5. Bibcode:1999PNAS...96.3611N. doi:10.1073/pnas.96.7.3611. PMC 22342. PMID 10097085.
- ^ Lobert, Jurgen; Keene, Willian; Yevich, Jennifer (1999). "Global chlorine emissions from biomass burning: Reactive Chlorine Emissions Inventory". Journal of Geophysical Research: Atmospheres. 104 (D7): 8373–8389. Bibcode:1999JGR...104.8373L. doi:10.1029/1998JD100077.
- ^ "ALMA and Rosetta Detect Freon-40 in Space".
- ^ "ALMA and Rosetta Detect Freon-40 in Space - Dashing Hopes that Molecule May be Marker of Life". eso.org. Retrieved 3 October 2017.
- ^ "Chloromethane". American Chemical Society. Retrieved 2022-05-13.
- ^ Fabian P, Borchers R, Leifer R, Subbaraya BH, Lal S, Boy M (1996). "Global stratospheric distribution of halocarbons". Atmospheric Environment. 30 (10/11): 1787–1796. Bibcode:1996AtmEn..30.1787F. doi:10.1016/1352-2310(95)00387-8.
- ^ Zhang W, Jiao Y, Zhu R, Rhew RC (2020). "Methyl Chloride and Methyl Bromide Production and Consumption in Coastal Antarctic Tundra Soils Subject to Sea Animal Activities". Environmental Science & Technology. 54 (20): 13354–13363. Bibcode:2020EnST...5413354Z. doi:10.1021/acs.est.0c04257. PMID 32935983. S2CID 221745138.
- ^ Carpenter LJ, Reimann S, Burkholder JB, Clerbaux C, Hall BD, Hossaini R, Laube JC, Yvon-Lewis SA (2014). "Update on ODSs and Other Gases of Interest to the Montreal Protocol". WMO (World Meteorological Organization), Scientific Assessment of Ozone Depletion: 2014, Global Ozone Research and Monitoring Project.
- ^ Lyman, Warren; Rosenblatt, David; Reehl, Wiliam (1982). Handbook of chemical property estimation methods. ISBN 9780070391758.
- ^ Agency for Toxic Substances and Disease Registry (ATSDR) (1990). "Toxicological profile for chloromethane".
{{cite journal}}: Cite journal requires|journal=(help) - ^ Borchers R, Gunawardena R, Rasmussen RA (1994). "Long term trend of selected halogenated hydrocarbons": 259–262.
{{cite journal}}: Cite journal requires|journal=(help) - ^ Crutzen PJ, Gidel LT (1983). "The tropospheric budgets of the anthropogenic chlorocarbons CO, CH4, CH3Cl and the effect of various NOx sources on tropospheric ozone". Journal of Geophysical Research. 88: 6641–6661. doi:10.1029/JC088iC11p06641.
External links
- International Chemical Safety Card 0419
- NIOSH Pocket Guide to Chemical Hazards. "#0403". National Institute for Occupational Safety and Health (NIOSH).
- Toxicological information
- Concise International Chemical Assessment Document 28 on chloromethane
- IARC Summaries & Evaluations Vol. 71 (1999)
- Ohligschläger et al. (2020). Chloromethanes. In Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a06_233.pub4