Question Bank › Organic Chemistry › Reagents, Reaction Mechanisms & Named Reactions › ABC26OR0849The order of nucleophilicity of the following anions in a SN 2 reaction is: P Q R S · ABC26OR0849 Subject: Organic Chemistry · Chapter: Reagents, Reaction Mechanisms & Named Reactions · Topic: Reagents, Reaction Mechanisms & Named Reactions – General · Exam: JAM 2005-2022 · Marks: 2 · Difficulty: Hard
The order of nucleophilicity of the following anions in a $\mathrm{S}_{\mathrm{N}} 2$ reaction is: P Q R S
(a) $\mathrm{Q} > \mathrm{R} > \mathrm{S} > \mathrm{P}$
(b) $\mathrm{Q} > \mathrm{P} > \mathrm{R} > \mathrm{S}$
(c) $\mathrm{Q} > \mathrm{R} > \mathrm{P} > \mathrm{S}$
(d) $\mathrm{P} > \mathrm{S} > \mathrm{R} > \mathrm{Q}$
Answer Answer: B ✓ checked by 4AB · confidence high
Explanation PhS⁻ (Q) is the most nucleophilic (soft, polarisable). PhO⁻ (P) comes next, then p-nitrophenoxide (R) and 2,4-dinitrophenoxide (S), which are less nucleophilic as their charge is delocalised. Q > P > R > S (b).
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