1,1,1-Trichloroethane

1,1,1-Trichloroethane, or methyl chloroform is an organic compound with the formula CH₃CCl₃. It is also known as chlorothene (a trade name from the 1950s). It is a colourless, heavy liquid that was previously used as a solvent but banned after it was discovered to harm the ozone layer.

Methyl chloroform is a chlorinated derivative of ethane and an isomer of 1,1,2-Trichloroethane (CHCl₂CH₂Cl). The 1,1,2-Trichloroethane isomer is less known, so "trichloroethane" often just refers to 1,1,1-Trichloroethane. It should also not be confused with trichloroethylene, another industrial solvent.

It is a liquid at 25 degrees Celsius, at standard atmosphere (a pressure).

History

1,1,1-Trichloroethane was discovered by the French chemist Henri Victor Regnault. It was used as an experimental anaesthetic in the 1880s, but this practice was dropped because it was hard to produce back then.

Preparation

Trichloroethane can be produced in a two-step process from vinyl chloride. Vinyl chloride reacts with hydrogen chloride to make 1,1-dichloroethane (this reaction is called Markovnikov addition). This chemical is then reacted with chlorine gas under ultraviolet light to make 1,1,1-trichloroethane (photochlorination). This reaction is regioselective: it makes mostly 1,1,1-trichloroethane and only small amounts of the 1,1,2-trichloroethane isomer. The selection can be improved with the right catalyst or solvent.

Uses

Before being banned for its harmful effects on the ozone layer, Trichloroethane was commonly used as a cleaning fluid in both homes and industry. Industrial uses include metal degreasing (cleaning metals from oils and grease), similar to trichloroethylene (TCE). Trichloroethane was introduced to metal cleaning as a less toxic alternative to TCE. One other common use of Trichloroethane was for washing photographic film. Most uses for trichloroethane used carbon tetrachloride previously.

Household uses for trichloroethane included stain removers, correction fluids and aerosols.