JEE Advanced 2017 · Paper 2 · Chemistry Q11

ChemistryMultiple correct+4 / -2Question 29 of 54

For the following compounds, the correct statement(s) with respect to nucleophilic substitution reactions is(are)

I and III follow

S_N1

mechanism

I and II follow

S_N2

mechanism

Compound IV undergoes inversion of configuration

The order of reactivity for I, III and IV is: IV > I > III

Answer and worked solution

Official answer: A, B, C

(A) Benzyl bromide (I) and tert-butyl bromide (III) both form stabilised cations (benzylic and tertiary), so they can follow $S_N1$ . True.
(B) Benzyl bromide and (bromomethyl)cyclohexane (II) are primary and unhindered at the carbon, so they react by $S_N2$ . True.
(C) (1-Bromoethyl)benzene (IV) is a chiral secondary benzylic halide. Under $S_N2$ conditions it reacts with inversion of configuration. True.
(D) For ionisation, the order IV > I > III is not clear-cut; the tertiary III is also very reactive by $S_N1$ . That is why the key accepts either answer.

Answer: (A), (B), (C) (the key accepts ABC or ABCD)

JEE Advanced 2017 · Paper 2, Chemistry question 11