Question

Choose the most reasonable reaction intermediate for the following reaction:

A.

B.

C.

D. None of these

Answer 1

Hint: 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.