Question

Choose the most reasonable reaction intermediate for the following reaction:

A.
B.
C.
D. None of these

Answer 1

The reaction given above generally based on the concept of aldol condensation which occurs in aldehydes and the necessary condition for aldol condensation is presence of $\alpha$ hydrogens with a dilute base which gives $\beta$ hydroxy aldehydes known by the name aldols.

Complete step-by-step answer:
In aldol condensation enolate ions react with a carbonyl compound to form $\beta$- hydroxy ketones or $\beta$- hydroxy aldehydes then dehydration occurs which give conjugated enone.
To choose the most stable intermediate for the given reaction we have to follow the following steps:
1. Break the bond between$\alpha$and $\beta$ carbon and attack of $O{{H}^{-}}$ $O{{H}^{-}}$ion on them which can be shown as follows:

2. After the attacking of hydroxide ion retro aldol condensation takes place which opens the ring and the structure will be shown as:

3. After this step again condensation process is done which again reform it in ring shape which can be shown as:

Hence by observing the whole reaction we can consider that the option C is the correct answer, this is the intermediate in the given reaction.

Note: Aldol condensations play a very important role in organic synthesis as it creates a path to form carbon-carbon bonds. When the same type of reaction occurs with two different types of carbonyl compounds then this type of reactions are known by the name cross aldol condensation.