Haloform Reaction of Methyl Ketones

The haloform reaction is a variation of α-halogenation. Under basic conditions for enolate formation of a methyl ketone, halogenation of the α-carbon continues until its supply of hydrogens is exhausted. The resulting trihalo-derivative is unstable, undergoing an acyl type substitution resulting in formation of carboxylate and haloform. The iodoform version of this reaction is used as a qualitative test for methyl ketones. Yellow iodoform precipitate convincingly indicates upon reaction with iodine the presence of a methyl ketone.