Chloromethane

Chloromethane is an abundant organohalogen, anthropogenic or natural, in the atmosphere. Natural sources produce an estimated 4,100,000,000 kg/yr.{{cite book|title=Naturally Occurring Organohalogen Compounds|editor=

Kinghorn, A. Douglas. |editor2=Falk, Heinz |editor3=Gibbons, Simon |editor4=Asakawa, Yoshinori |editor5=Liu, Ji-Kai |editor6=Dirsch, Verena M. |publisher=Springer Nature|location=Switzerland|year=2023|

isbn= 978-3-031-26629-4|author=Gribble, Gordon|series=Progress in the Chemistry of Organic Natural Products }}

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.{{cite journal |vauthors=Scarratt MG, Moore RM| year = 1996 | title = Production of Methyl Chloride and Methyl Bromide in Laboratory Cultures of Marine Phytoplankton | journal = Mar Chem | volume = 54 | pages = 263–272 | doi = 10.1016/0304-4203(96)00036-9 | issue = 3–4| bibcode = 1996MarCh..54..263S }}{{cite journal |vauthors=Scarratt MG, Moore RM| year = 1998 | title = Production of Methyl Bromide and Methyl Chloride in Laboratory Cultures of Marine Phytoplankton II | journal = Mar Chem | volume = 59 | pages = 311–320 | doi = 10.1016/S0304-4203(97)00092-3 | issue = 3–4| bibcode = 1998MarCh..59..311S }} An extensive study of 30 species of polar macroalgae revealed the release of significant amounts of CH₃Cl in only Gigartina skottsbergii and Gymnogongrus antarcticus.{{cite journal | author = Laturnus F | year = 2001 | title = Marine Macroalgae in Polar Regions as Natural Sources for Volatile Organohalogens | journal = Environ Sci Pollut Res | volume = 8 | pages = 103–108 | doi = 10.1007/BF02987302 | pmid = 11400635 | issue = 2| bibcode = 2001ESPR....8..103L | s2cid = 570389 }}

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.{{cite journal |vauthors=Ni X, Hager LP| year = 1998 | title = cDNA Cloning of Batis maritima Methyl Chloride Transferase and Purification of the Enzyme | journal = Proc Natl Acad Sci USA | volume = 95 | pages = 12866–71 | doi = 10.1073/pnas.95.22.12866 | pmid = 9789006 | issue = 22 | pmc = 23635| bibcode = 1998PNAS...9512866N | doi-access = free }} 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.{{cite journal |vauthors=Ni X, Hager LP| year = 1999 | title = Expression of Batis maritima Methyl Chloride Transferase in Escherichia coli | journal = Proc Natl Acad Sci USA | volume = 96 | pages = 3611–5 | doi = 10.1073/pnas.96.7.3611 | pmid = 10097085 | issue = 7 | pmc = 22342| bibcode = 1999PNAS...96.3611N | doi-access = free }}

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.{{cite journal |title= Global chlorine emissions from biomass burning: Reactive Chlorine Emissions Inventory |journal= Journal of Geophysical Research: Atmospheres |volume= 104 |pages= 8373–8389 |last1= Lobert |first1= Jurgen |last2= Keene |first2=Willian |last3= Yevich |first3=Jennifer |doi=10.1029/1998JD100077 |year=1999 |issue= D7 |bibcode=1999JGR...104.8373L|doi-access= free }}

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.{{Cite web | url=https://www.eso.org/public/images/eso1732e/ |title = ALMA and Rosetta Detect Freon-40 in Space}} The detections reveal that chloromethane can be formed in star-forming regions before planets or life is formed.{{cn|date=October 2023}}

File:ALMA and Rosetta Detect Freon-40 in Space.jpg

Chloromethane (originally called "chlorohydrate of methylene") was among the earliest organochlorine compounds to be discovered when it was synthesized by French chemists Jean-Baptiste Dumas and Eugène-Melchior Péligot in 1835 by boiling a mixture of methanol, sulfuric acid, and sodium chloride.{{Cite book |last1=Crochard (París) |url=https://books.google.com/books?id=yCpCAAAAcAAJ&pg=PA25 |title=Annales de chimie et de physique |last2=Arago |first2=François |last3=Gay-Lussac |first3=Joseph Louis |date=1835 |publisher=Chez Crochard |language=fr}} This method is the forerunner for that used today, which uses hydrogen chloride instead of sulfuric acid and sodium chloride.{{Cite web |title=Chloromethane |url=https://www.acs.org/content/acs/en/molecule-of-the-week/archive/c/chloromethane.html |access-date=2022-05-13 |website=American Chemical Society |language=en}}

Chloromethane is produced commercially by treating methanol with hydrochloric acid or hydrogen chloride, according to the chemical equation:{{Ullmann | last1 = Rossberg | first1 = M. | last2 = Lendle | first2 = W. | last3 = Pfleiderer | first3 = G. | last4 = Tögel | first4 = A. | last5 = Dreher | first5 = E. L. | last6 = Langer | first6 = E. | last7 = Rassaerts | first7 = H. | last8 = Kleinschmidt | first8 = P. | last9 = Strack | first9 = H. | last10 = Cook | first10 = R. | last11 = Beck | first11 = U. | last12 = Lipper | first12 = K.-A. | last13 = Torkelson | first13 = T.R.| last14 = Löser | first14 = E. | last15 = Beutel | first15 = K.K. | last16 = Mann | first16 = T. | title= Chlorinated Hydrocarbons| year = 2006 | isbn = 3527306730 | doi=10.1002/14356007.a06_233.pub2 | pmc = }}

: 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.

: {{Chem2|CH4 + Cl2 -> CH3Cl + HCl}}

: {{Chem2|CH3Cl + Cl2 -> CH2Cl2 + HCl}}

: {{Chem2|CH2Cl2 + Cl2 -> CHCl3 + HCl}}

: {{Chem2|CHCl3 + Cl2 -> CCl4 + HCl}}

File:CH3Cl_mm.png) at stations around the world. Abundances are given as pollution free monthly mean mole fractions in parts per trillion.]]

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.{{cite journal|vauthors=Fabian P, Borchers R, Leifer R, Subbaraya BH, Lal S, Boy M |title=Global stratospheric distribution of halocarbons |journal= Atmospheric Environment |volume=30 |number=10/11 |pages=1787–1796 |date=1996|doi=10.1016/1352-2310(95)00387-8 |bibcode=1996AtmEn..30.1787F }}{{cite journal|vauthors=Zhang W, Jiao Y, Zhu R, Rhew RC |title= Methyl Chloride and Methyl Bromide Production and Consumption in Coastal Antarctic Tundra Soils Subject to Sea Animal Activities|journal= Environmental Science & Technology |volume=54 |number=20 |pages=13354–13363 |date=2020|doi=10.1021/acs.est.0c04257|pmid= 32935983|bibcode= 2020EnST...5413354Z|s2cid= 221745138}}{{cite journal|vauthors=Carpenter LJ, Reimann S, Burkholder JB, Clerbaux C, Hall BD, Hossaini R, Laube JC, Yvon-Lewis SA |title= Update on ODSs and Other Gases of Interest to the Montreal Protocol|journal= WMO (World Meteorological Organization), Scientific Assessment of Ozone Depletion: 2014, Global Ozone Research and Monitoring Project |date=2014|url=https://www.esrl.noaa.gov/csl/assessments/ozone/2014/summary/ch1.html}}

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.{{cite book|last1=Lyman |first1=Warren |authorlink1=XPTO |last2=Rosenblatt |first2=David |authorlink2=XPTO |last3=Reehl |first3=William |date=1982 |title=Handbook of chemical property estimation methods|publisher=McGraw-Hill |isbn=9780070391758 |url=https://archive.org/details/handbookofchemic0000lyma |url-access=registration }}{{cite book|author=Agency for Toxic Substances and Disease Registry |url=https://www.ncbi.nlm.nih.gov/books/NBK600824/ |title=Toxicological profile for chloromethane |series=Agency for Toxic Substances and Disease Registry (ATSDR) Toxicological Profiles |date=1990|publisher=Agency for Toxic Substances and Disease Registry (US) |pmid=38412209 }}

The amount of methyl chloride in the stratosphere is estimated to be 2{{e|6}} tonnes per year, representing 20–25% of the total amount of chlorine that is emitted to the stratosphere annually.{{cite journal|vauthors=Borchers R, Gunawardena R, Rasmussen RA |title=Long term trend of selected halogenated hydrocarbons |pages=259–262 |date=1994 |url=https://ntrs.nasa.gov/citations/19950004240 |id=19950004240 |journal=Ozone in the Troposphere and Stratosphere |publisher=NASA}}{{cite journal|vauthors=Crutzen PJ, Gidel LT |title=The tropospheric budgets of the anthropogenic chlorocarbons CO, CH4, CH3Cl and the effect of various NOx sources on tropospheric ozone |journal=Journal of Geophysical Research |volume=88 |pages=6641–6661 |date=1983|doi=10.1029/JC088iC11p06641 }}

{{More citations needed section|date=February 2023}}

Large scale use of chloromethane is for the production of dimethyldichlorosilane and related organosilicon compounds. 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.

Chloromethane was widely used as a refrigerant during the 1920s and 1930s, before being replaced by safer alternatives such as hydrofluorocarbons. In the late 1920s, some manufacturers promoted methyl chloride as a safer and less odorous option compared to sulfur dioxide and ammonia.{{cite web |last=Hand |first=Greg |title=Refrigeration Was A Wonderful Invention When It Wasn't Trying To Kill You |website=Cincinnati Magazine |date=4 April 2023 |url=https://www.cincinnatimagazine.com/article/refrigeration-was-a-wonderful-invention-when-it-wasnt-trying-to-kill-you/ |access-date=15 May 2025}}{{cite web |title=Toxicological Profile for Chloromethane |url=https://www.ncbi.nlm.nih.gov/books/NBK600826/ |publisher=Agency for Toxic Substances and Disease Registry |access-date=15 May 2025 |date=September 2023}}https://archive.org/details/sim_consumer-reports_1936-07_1_3/page/5/mode/1up Consumers Union Reports, Vol. 1, No. 3, July 1936, p. 5. 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.

Chloromethane was also once used for producing the lead-based gasoline additive tetramethyllead.{{citation needed|date=May 2025}}

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.

• bromomethane
• dichloromethane
• trichloromethane
• tetrachloromethane

{{reflist}}

• {{ICSC|0419|04}}
• {{PGCH|0403}}
• [https://web.archive.org/web/20070927210420/http://www.inchem.org/documents/sids/sids/CLMETHANE.pdf Data sheet at inchem.org]
• [http://www.inchem.org/documents/pims/chemical/metchlor.htm Toxicological information]
• [https://web.archive.org/web/20070927195226/http://www.eco-usa.net/toxics/clmethan.shtml Information about chloromethane]
• [http://www.inchem.org/documents/cicads/cicads/cicad28.htm Concise International Chemical Assessment Document 28 on chloromethane]
• [http://www.inchem.org/documents/iarc/vol71/026-methylchloride.html 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

{{halomethanes}}

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Category:Greenhouse gases

Category:Halogenated solvents

Category:Halomethanes

Category:IARC Group 3 carcinogens

Category:Chloroalkanes

Category:Refrigerants

Category:Chlorine-containing natural products

Category:Methylating agents

Category:Ozone-depleting chemical substances