Chemistry - GOC Question with Solution | TestHub
When a base abstract H bonded to carbon, carbanion is formed
Carbon bearing negative charge is sp3 hybridised, undergo fluxional inversion.
Consider the following reaction-
A carbanion is formed in the first step of above reaction which finally gives the desired product. Which is the most likely position of carbanion responsible for the above reaction is ______?
Answer:
Solution:
OH⁻ first abstracts the most acidic α-hydrogen adjacent to the carbonyl group.
Removal of H from position 2 forms a resonance-stabilized enolate (carbanion).
This carbanion is stabilized by conjugation with the C=O group, making it the most favorable intermediate.
The enolate then attacks the double bond intramolecularly, leading to ring closure.
Finally, elimination of Br⁻ and rearrangement gives the fused cyclic product shown.
Therefore, the carbanion is formed at position 2, so the correct answer is 2.