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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Necrophobos on March 13, 2011, 02:18:43 PM

Title: Iodoform reaction
Post by: Necrophobos on March 13, 2011, 02:18:43 PM

Hello, I have a doubt regarding the iodoform reaction and am hoping someone would be able to clarify it for me.

Why is this reaction a typical reaction of methyl ketones?

Thanks in advance ;)

Title: Re: Iodoform reaction
Post by: stewie griffin on March 13, 2011, 02:26:13 PM

You question is a bit nebulous. The iodoform reaction is specific to methyl ketones, so I'm not sure how one could answer why the iodoform reaction is a typical reaction of methyl ketones.
Perhaps you meant to ask why methyl ketones are able to undergo the iodoform reaction? If so, consider ability to enolize, and also the electrophilicity of a ketone bearing a trihalomethyl group.

Title: Re: Iodoform reaction
Post by: Necrophobos on March 13, 2011, 03:00:22 PM

Well I'm new to organic chemistry so I really don't know about the ability to enolize and electrophilicity :/

What I meant though was why do methyl ketones react in the iodoform reaction and, for example, diethyl ketone doesn't. But I've read some things meanwhile and am guessing it's because of the formation of a carbonyl group, that reacts with a base, later forming the carboxyl group.

Title: Re: Iodoform reaction
Post by: zolarpwr on March 14, 2011, 07:42:01 PM

You're asking the right question. That's the key to understanding.

Now ask yourself what would form from diethyl ketone under those conditions (iodine and base). Compare its electrophilicity with what you would get with the methyl ketone, before hydrolysis. What would the carbon group in place of the extra halogen do?

Title: Re: Iodoform reaction
Post by: adianadiadi on March 19, 2011, 03:45:55 AM

Iodoform, CHI₃ is only formed when there are alpha methyl groups i.e., adjacent to the carbonyl carbon. There must be three hydrogens to be replaced by iodine atoms. Otherwise no iodoform is going to be formed.

Title: Re: Iodoform reaction
Post by: Necrophobos on March 21, 2011, 02:16:36 PM

Thanks everyone, I think I understood it ;)