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Chloromethane, also called methyl chloride, Refrigerant-40, 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. 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.

Stereo, skeletal formula of chloromethane with all explicit hydrogens added
Ball and stick model of chloromethane
Spacefill model of chloromethane
IUPAC name
Other names
  • Refrigerant-40
  • R-40[1]
  • Methyl chloride[1]
  • Monochloromethane[1]
3D model (JSmol)
ECHA InfoCard 100.000.744
EC Number 200-817-4
MeSH Methyl+Chloride
RTECS number PA6300000
UN number 1063
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))
940 nmol Pa−1 kg−1
-32.0·10−6 cm3/mol
1.9 D
234.36 J K−1 mol−1
−83.68 kJ mol−1
−764.5–−763.5 kJ mol−1
Main hazards carcinogen
Safety data sheet See: data page
GHS pictograms GHS02: Flammable GHS08: Health hazard
GHS signal word DANGER
H220, H351, H373
P210, P281, P410+403
NFPA 704
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored 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):
1800 mg/kg (oral, rat)[1]
5.3 mg/L/4 h (inhalation, rat)[1]
72,000 ppm (rat, 30 min)
2200 ppm (mouse, 6 hr)
2760 ppm (mammal, 4 hr)
2524 ppm (rat, 4 hr)[4]
20,000 ppm (guinea pig, 2 hr)
14,661 ppm (dog, 6 hr)[4]
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 100 ppm C 200 ppm 300 ppm (5-minute maximum peak in any 3 hours)[3]
REL (Recommended)
IDLH (Immediate danger)
Ca [2000 ppm][3]
Related compounds
Related alkanes
Related compounds
Supplementary data page
Refractive index (n),
Dielectric constantr), etc.
Phase behaviour
Except where otherwise noted, 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 is the most abundant organohalogen, anthropogenic or natural, in the atmosphere. It is a constituent of tobacco smoke.[5]


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.[6][7] An extensive study of 30 species of polar macroalgae revealed the release of significant amounts of CH3Cl in only Gigartina skottsbergii and Gymnogongrus antarcticus.[8]


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.[9] 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.[9][10]

Interstellar detectionsEdit

Chloromethane has been detected in the low-mass Class 0 protostellar binary, IRAS 162932422, 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.[11] The detections reveal that chloromethane can be formed in star-forming regions before planets or life is formed.

Freon-40 has been detected in space.[12]


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 (662 °F).

A smaller amount of chloromethane is produced by heating a mixture of methane and chlorine to over 400 °C (752 °F). However, this method also results in more highly chlorinated compounds such as dichloromethane, chloroform, and carbon tetrachloride and is usually only used when these other products are also desired.

Dispersion in the environmentEdit

Most of the methyl chloride present in the environment ends up being released to the atmosphere. After being released into the air, the life of this substance in the atmosphere varies from one to three years.[13]

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.[14][15]

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.[16][17]

Sugarcane and the emission of methyl chlorideEdit

In the sugarcane cultivation, it is common to use potassium sources containing high concentrations of chlorine, as is the case of potassium chloride (KCl). Consequently, sugarcane ends up absorbing high concentrations of this substance.[18]

In the sugarcane industry, the sugarcane is usually burned in the power cogeneration process. Thus, by virtue of the amount of chlorine absorbed by the cane, this burning ends up emitting methyl chloride to the atmosphere.[19]

Destruction of the ozone layerEdit

The burning of biomass, as for example sugarcane, appears to be the largest single source of methyl chloride (CH3Cl) present in atmosphere. In addition to this compound, chlorine is also emitted in the inorganic form (Cl) during this burning.[19] When methyl chloride (CH3Cl) is emitted and reaches the stratosphere ends up being very harmful for the ozone layer, considering that the chlorine when combined with the ozone molecule generates a catalytic reaction leading to the breakdown of ozone links.[19]

1ª Step: Cl + O3 → ClO + O2
2ª Step: ClO + O → Cl + O2
Net: O3 + O → 2 O2

After each reaction, chlorine starts a destructive cycle with another ozone molecule. In this way, a single chlorine atom can destroy thousands of ozone molecules. As these molecules are being broken, they are unable to absorb the ultraviolet rays. As a result, the UV radiation is more intense on the surface of the Earth.[19]


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.


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.


  1. ^ 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
  2. ^ "Methyl Chloride - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Retrieved 23 June 2012.
  3. ^ a b c d e NIOSH Pocket Guide to Chemical Hazards. "#0403". National Institute for Occupational Safety and Health (NIOSH).
  4. ^ a b "Methyl chloride". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  5. ^ Talhout, Reinskje; Schulz, Thomas; Florek, Ewa; Van Benthem, Jan; Wester, Piet; Opperhuizen, Antoon (2011). "Hazardous Compounds in Tobacco Smoke". International Journal of Environmental Research and Public Health. 8 (12): 613–628. doi:10.3390/ijerph8020613. ISSN 1660-4601. PMC 3084482. PMID 21556207.
  6. ^ 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.
  7. ^ 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.
  8. ^ 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.
  9. ^ 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. doi:10.1073/pnas.95.22.12866. PMC 23635. PMID 9789006.
  10. ^ Ni X, Hager LP (1999). "Expression of Batis maritima Methyl Chloride Transferase in Escherichia coli". Proc Natl Acad Sci USA. 96 (7): 3611–5. doi:10.1073/pnas.96.7.3611. PMC 22342. PMID 10097085.
  11. ^ "ALMA and Rosetta Detect Freon-40 in Space".
  12. ^ "ALMA and Rosetta Detect Freon-40 in Space - Dashing Hopes that Molecule May be Marker of Life". Retrieved 3 October 2017.
  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.
  14. ^ Lyman, Warren; Rosenblatt, David; Reehl, Wiliam (1982). Handbook of chemical property estimation methods.
  15. ^ Agency for Toxic Substances and Disease Registry (ATSDR) (1990). "Toxicological profile for chloromethane".
  16. ^ Borchers R, Gunawardena R, Rasmussen RA (1994). "Long term trend of selected halogenated hydrocarbons": 259–262.
  17. ^ 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.
  18. ^ Yive, N. S .C. K., Tiroumalechetty, M (2008). "Dioxin levels in fly ash coming from the combustion of bagasse". Journal of Hazardous Materials. 155: 179–182.CS1 maint: Multiple names: authors list (link)
  19. ^ a b c d Lobert, Jurgen; Keene, Willian; Yevich, Jennifer. "Global chlorine emissions from biomass burning: Reactive Chlorine Emissions Inventory" (PDF). Retrieved 11 March 2019. External link in |publisher= (help)

External linksEdit