Aldol Condensation

by James

Description: The aldol condensation is a reaction between an enolate (or enol) and an aldehyde or ketone that leads to the formation of a new carbon-carbon double bond. This is the product if an aldol addition reaction is heated for prolonged periods. The reaction is called a “condensation” because one molecule of water is formed from the two reactants.
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{ 6 comments… read them below or add one }

David Carnevale March 6, 2014 at 3:11 am

Are there any conditions in which the ketone and alcohol remain and the double bond does not form in the final elimination step?

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James May 26, 2014 at 4:00 pm

Yes – that’s “aldol addition”. Typically one avoids using heat in that process.

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Petr Menzel May 26, 2014 at 3:09 am

Hi, is the “heat” always important? Or can I use another way for condensation? Thx, P.

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James May 26, 2014 at 4:01 pm

Hi Petr – for aldol condensation, heat tends to favour elimination of water. If one wants to perform the aldol condensation, the best way to go about it is to heat the reaction mixture. To avoid the elimination, and to just perform an aldol addition reaction, typically one uses lower temperatures.

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Rich Aversa November 18, 2014 at 5:19 am

In the intramolecular reaction, the ketone you deprotonated has a primary and a secondary alpha carbon, so it has two different enolate forms. The conditions used would encourage formation of the “thermodynamic enolate”, i.e. the more substituent pi bond. Thus, the cyclic product would look quite different. For instance the remaining ketone would not “straddle” the ring but “hang off”, connected to its now tertiary alpha carbon. As I’ve seen it in other sources, a 1,6-diketone should yield a five-membered ring. Is this correct?

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James November 18, 2014 at 10:17 am

While that enolate is in fact the more stable “thermodynamic” enolate, it would form a 4-membered ring, not a 5-membered ring. That’s why it doesn’t happen.

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