A) \[P<R<S<Q\]
B) \[R<P<S<Q\]
C) \[R<P<Q<S\]
D) \[P<R<Q<S\]
Correct Answer: B
Solution :
Allyl and benzyl carbanions, due to resonance, are more stable than the primary alkyl carbanion, which is more stable than secondary carbanion as electron releasing group (alkyl group) decreases the stability of carbanions. Between, allyl and benzyl carbanions, benzyl carbanion is more resonance stabilise than the allyl carbanion. Thus, the ascending order of stability is \[\underset{(R)}{\mathop{\underset{{{2}^{o}}}{\mathop{{{(C{{H}_{3}})}_{2}}}}\,}}\,\bar{C}H<\underset{(P)}{\mathop{\underset{{{1}^{o}}}{\mathop{CH_{3}^{-}}}\,}}\,<\underset{\begin{smallmatrix} \text{allyl}\,\text{carbanion} \\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,(S) \end{smallmatrix}}{\mathop{{{H}_{2}}\bar{C}-CH=C{{H}_{2}}}}\,\] \[\underset{\begin{smallmatrix} (benzyl\,carbanion) \\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(Q) \end{smallmatrix}}{\mathop{<\,{{C}_{6}}{{H}_{5}}CH_{2}^{-}}}\,\]
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