Alkyl Halides - Result Question 22

22. $KI$ in acetone, undergoes $S _N 2$ reaction with each $P, Q, R$ and $S$. The rates of the reaction vary as

(2013 Adv.)

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(a) $P>Q>R>S$

(b) $S>P>R>Q$

(c) $P>R>Q>S$

(d) $R>P>S>Q$

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Answer:

Correct Answer: 22. (b)

Solution:

  1. PLAN: Acetone is an aprotic solvent and can dissolve both the nucleophile and the substrate and thus $S _N 2$ reaction is favoured. Also

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Thus, reactivity order is $S>P>R>Q$