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Chloromethane was once widely used as a refrigerant¹, but it has long since been replaced by substances that are less toxic and less harmful to the ozone layer in Earth’s atmosphere.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.