Chemical Forums

Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Cooper on March 07, 2013, 05:09:44 PM

Title: NaOH & Cl2, Acid on Ketones
Post by: Cooper on March 07, 2013, 05:09:44 PM
Hi,

Can anyone explain this mechanism? I have been trying to figure it out :s

Thanks

Title: Re: NaOH & Cl2, Acid on Ketones
Post by: Dan on March 08, 2013, 03:01:26 AM
NaOH is a strong base.

To get started, what could it deprotonate?
Title: Re: NaOH & Cl2, Acid on Ketones
Post by: Cooper on March 08, 2013, 12:41:46 PM
NaOH is a strong base.

To get started, what could it deprotonate?

It could deprotonate the alpha hydrogen, but how do you know it won't attack the carbonyl instead?

In general, how can you distinguish a base from a nucleophile?
Title: Re: NaOH & Cl2, Acid on Ketones
Post by: Dan on March 08, 2013, 12:43:50 PM
It can and will do both. The key thing to remember is that both processes are reversible. Addition of hydroxide to the ketone is not productive. α-Deprotonation generates the enolate, which is nucleophilic. Can you see any electrophiles in your mixture?
Title: Re: NaOH & Cl2, Acid on Ketones
Post by: Cooper on March 08, 2013, 12:52:00 PM
It can and will do both. The key thing to remember is that both processes are reversible. Addition of hydroxide to the ketone is not productive. α-Deprotonation generates the enolate, which is nucleophilic. Can you see any electrophiles in your mixture?

It could attack the chlorine molecule and break it heterolytically, right? It would form acyl chloride. Then would carbonyl addition-elimination occur? The OH could then attack the carbonyl carbon, the electrons in the double bond would go to the oxygen, then come back down and reform the pi bond, kicking out Cl.

Is that what happens?
Title: Re: NaOH & Cl2, Acid on Ketones
Post by: discodermolide on March 08, 2013, 06:39:21 PM
Have a look here and see if it fits with your reaction.
http://en.wikipedia.org/wiki/Haloform_reaction (http://en.wikipedia.org/wiki/Haloform_reaction)
Title: Re: NaOH & Cl2, Acid on Ketones
Post by: Cooper on March 14, 2013, 05:51:27 PM
Have a look here and see if it fits with your reaction.
http://en.wikipedia.org/wiki/Haloform_reaction (http://en.wikipedia.org/wiki/Haloform_reaction)

Yeah thanks, the reaction was a couple chapters ahead of where it was asked about in the book for some reason. :P