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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: jokulsa on October 07, 2014, 05:00:21 AM

Title: Ketones
Post by: jokulsa on October 07, 2014, 05:00:21 AM

The iodoform test only reacts with methyl ketones. What's the main difference between a methyl ketone and other ketones?

Title: Re: Ketones
Post by: mjc123 on October 07, 2014, 05:14:13 AM

It has a methyl group attached to the carbonyl carbon.
The three hydrogens of the methyl group can be substituted by I in the presence of base, and CI₃^- (stabilised by the 3 electron-withdrawing halogens) can act as a leaving group in an acyl substitution reaction, then being protonated to give CHI₃. Other alkyl groups may be halogenated at the α position, but the partially-halogenated alkyl groups do not act as leaving groups. (See "haloform reaction" on Wikipedia)