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Describe the following:
(i) Cross aldol condensation
(ii) Decarboxylation

Last updated date: 20th Jun 2024
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Hint The answer here is dependent on the basic concept of organic chemistry which deals with the reaction mechanism where aldol condensation gives the $\beta -$ hydroxy aldehyde or $\beta -$ hydroxy ketone and decarboxylation is the removal of carboxyl group.

Complete answer:
Let us now see in detail about these two reactions given and write their mechanism of reaction.
(i) Aldol condensation:
Aldol condensation as the name itself says is the condensation of an enol or enolate ion with the carbonyl compound to form a $\beta -$ hydroxy aldehyde or $\beta -$ hydroxy ketone which is followed by dehydration to give a conjugated enone.
The step by step mechanism by citing an example as general reaction can be explained as shown below,
seo images

The carboxylic addition to the enol group reacts in a protonated form where the addition product is obtained which on dehydration yields the condensation product.
(ii) Decarboxylation is the chemical reaction which removes a carboxyl group with the release of carbon dioxide gas. Here, there is removal of one carbon atom which comes out as $C{{O}_{2}}$
The general reaction for this process is given as shown below,
seo images

Therefore, the product forms is the alkane and carbon dioxide in the above case

Note: Note that the aldol condensation takes place only if there is $\alpha -$ hydrogen atom because the aldol condensation requires the formation of the enolate ion or enol and the absence of$\alpha -$hydrogen do not give these intermediates.