Question

Which of the following second ion is more stable than the first ion:

• A.
• B.
• C.
• D.

Answer 1

Answer: (A)

(A) II : Acetylenic carbanion is more stable than vinylic carbanion because $sp$ hybridised carbon is more electronegative than $s{p}^2$ hybridised carbon.
(B) I : Benzyl carbanion is more stable ($4$ resonating structures) than allyl carbanion (two resonating structures).
(C) II : Secondary allyl carbanion is less stable than primary allyl carbanion.
(D) I : is aromatic carbanion and (II) is non aromatic carbanion. Aromatic carbanion is more stable than non-aromatic carbanion.