Haloform reaction
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The haloform reaction is the chemical reaction where a haloform (CHX3, where X = halogen) is produced by the exhaustive halogenation of a ketone with one methyl group (R–CO–CH3, where R = H, alkyl or aryl) in the presence of a base.
Procedure
The halogen is dissolved in a basic solution, such as NaOH. The solution is then cooled, as the reaction is very exothermic. A methyl ketone, such as acetone, methyl ethyl ketone, 2-pentanone is then added.
Alternatively, secondary alcohols having an alpha methyl group (such as isopropanol) can also be used, as these will be oxidised to the corresponding methyl ketone. The only primary alcohol and aldehyde to undergo this reaction are ethanol and acetaldehyde.
Uses
The reaction can be used to produce chloroform (CHCl3), bromoform (CHBr3), or iodoform (CHI3). Fluoroform (CHF3) cannot be produced via this route as the hypofluorite ion is too unstable to work.
Can also be used to detect ketones in an organic sample, iodoform test being the most convenient.
