Chloroform - Blog Posts
Molecule of the Day: Chloroform
Chloroform (CHCl3) is a colourless, dense liquid that is immiscible with water at room temperature and pressure. Popularised by movies and dramas, it is often cited as an incapacitating agent in popular culture.
Chloroform was used as a general anaesthetic due to its ability to depress the central nervous system, a property that was discovered in 1842. This produced a medically-induced coma, allowing surgeons to operate on patients without them feeling any pain.
However, chloroform was found to be associated with many side effects, such as vomiting, nausea, jaundice, depression of the respiratory system, liver necrosis and tumour formation, and its use was gradually superseded in the early 20th century by other anaesthetics and sedatives such as diethyl ether and hexobarbital respectively.
While chloroform has been implicated in several criminal cases, its use as an incapacitating agent is largely restricted to fiction; the usage of a chloroform-soaked fabric to knock a person out would take at least 5 minutes.
Chloroform is metabolised in the liver to form phosgene, which can react with DNA and proteins. Additionally, phosgene is hydrolysed to produced hydrochloric acid. These are believed to cause chloroform’s nephrotoxicity.
Chloroform is often used as a reagent to produce dichlorocarbene in situ via its reaction with a base like sodium tert-butoxide. This is a useful precursor to many derivatives. For example, the dichlorocarbene can be reacted with alkenes to form cyclopropanes, which can be difficult to synthesise otherwise.
Chloroform is industrially synthesised by the free radical chlorination of methane:
CH4 + 3 Cl2 –> CHCl3 + 3 HCl
It can also be synthesised by the reaction of acetone with sodium hypochlorite in bleach by successive aldol-like reactions:
