Question

This conversion can be achieved by :

• A. Dehydration, Hydrolysis
• B. Retro aldol and further condensation
• C. Perkin condensation & Clemmensen reduction
• D. Clemmensen and Perkin condensation

Answer 1

The correct option is B Retro aldol and further condensation

This given conversion is achieved by retro aldol and further self aldol condensation.

$\beta$-hydroxy ketone on reacting with strong base will undergo retro aldol reaction. It is a reverse of aldol reaction.

Initially the strong base will abstract the acidic proton from the $OH$ and forms a keto group which leads to $C-C$ bond breakage to form carbanion followed by proton abstraction.

Formed diketone from retro aldol reaction undergo self aldol condensation in presence of $O{H}^{-}$.
It is a symmetrical diketone. There are 2 possible ways to form enolate ion in this diketone.

Enolate formed from carbon (2) will leads to 4 membered ring which is less stable.

Enolate formed from carbon (1) will leads to 6 membered ring which is highly stable.
Thus, mechanism of intramolecular aldol condensation of the diketone compound is