August 23, 2021
I’m a long-known gas with many uses.
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Image of Chloromethane 3D Image of Chloromethane

Chloromethane, frequently called methyl chloride, is a colorless, toxic gas. It has been known since the early 19th century.

In 1835, prominent French chemists Jean-Baptiste Dumas of the École Polytechnique and Eugène Péligot of the Institut National Agronomique (both in Paris) teamed up to devise the first synthesis of chloromethane. They heated methanol and sodium chloride in the presence of sulfuric acid to produce the gas. Their synthesis was the forerunner of the primary modern manufacturing method, which uses hydrogen chloride in place of NaCl and H2SO4.

Chloromethane is found sparsely in nature. It is usually produced by the enzyme methyl chloride tranferase, which is present in wood-rotting fungi and salt marsh plants. As of 2020, chloromethane was the only organochlorine compound to have been detected in space, by both the Atacama Large Millimeter/submillimeter Array telescope in Chile and the Rosetta spacecraft.

Chloromethane was once widely used as a refrigerant1, but it has long since been replaced by substances that are less toxic and less harmful to the ozone layer in Earth’s atmosphere. Currently, it is used in industry as a reagent in chemical production, an extractant for oils and resins, a propellant in foam production, and a solvent in rubber manufacture and petroleum refining.

1. As a refrigerant, chloromethane was called Freon-40.

Chloromethane hazard information

Hazard class*GHS code and hazard statement
Flammable gases, category 1H220—Extremely flammable gasChemical Safety Warning
Gases under pressure (liquefied gas), category 3H280—Contains gas under pressure; may explode if heated Chemical Safety Warning
Carcinogenicity, category 2H351—Suspected of causing cancerChemical Safety Warning
Reproductive toxicity, category 2H361—Suspected of damaging fertility or the unborn childChemical Safety Warning
Specific target organ** toxicity, repeated exposure, inhalation, category 2H373—Causes damage to organs through prolonged or repeated exposure if inhaledChemical Safety Warning

*Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. 
Explanation of pictograms. 
**Central nervous system, liver, and/or urogenital tract.

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fast facts

CAS Reg. No.74-87-3
Methane, chloro-
Empirical formulaCH3Cl
Molar mass50.49 g/mol
AppearanceColorless gas
Boiling point–24 °C
Water solubility5.3 g/L
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