Match List-I with List-II.
| List-I | List-II |
|---|---|
| (A) Kinetics of the reaction of chloromethane with hydroxide ion | (I) First order kinetics |
| (B) Kinetics of the reaction of tert-butyl bromide with hydroxide ion | (II) Second order kinetics |
| (C) Stereochemical result of the reaction of (–)-2-bromooctane with sodium hydroxide | (III) Racemisation |
| (D) Stereochemical result of the hydrolysis of optically active 2-bromobutane through a planar carbocation | (IV) Inversion of configuration |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A-II, B-I, C-IV, D-III
In an SN2 reaction the nucleophile attacks as the halide leaves, in one step, from the side opposite to the halogen. In an SN1 reaction the halide first leaves in a slow step, giving a planar carbocation, which the nucleophile then attacks.
(A) Kinetics of the reaction of chloromethane with hydroxide ion — This matches (II) Second order kinetics. Methanol is formed by an SN2 reaction, so the rate depends on the concentration of both reactants: rate = k[CH3Cl][OH−].
(B) Kinetics of the reaction of tert-butyl bromide with hydroxide ion — This matches (I) First order kinetics. tert-Butyl alcohol is formed by an SN1 reaction; the slow step is the ionisation of the bromide, so the rate depends only on [tert-butyl bromide].
(C) Stereochemical result of the reaction of (–)-2-bromooctane with sodium hydroxide — This matches (IV) Inversion of configuration. This is the SN2 example: the –OH group takes the position opposite to the one the bromine had occupied, and (+)-octan-2-ol is formed.
(D) Stereochemical result of the hydrolysis of optically active 2-bromobutane through a planar carbocation — This matches (III) Racemisation. A carbocation means SN1; the sp2 carbocation is planar, so –OH attaches from either face and (±)-butan-2-ol, a racemic mixture, is formed.
NCERT (2026-27 edition):
6.7.1 Reactions of Haloalkanes – “The reaction between CH3Cl and hydroxide ion to yield methanol and chloride ion follows a second order kinetics, i.e., the rate depends upon the concentration of both the reactants.”
“…The reaction between tert- butyl bromide and hydroxide ion yields tert-butyl alcohol and follows the first order kinetics, i.e., the rate of reaction depends upon the concentration of only one reactant, which is tert- butyl bromide.”
“…When (–)-2-bromooctane is allowed to react with sodium hydroxide, (+)-octan-2-ol is formed with the –OH group occupying the position opposite to what bromide had occupied.”
“…This may be illustrated by hydrolysis of optically active 2-bromobutane, which results in the formation of (±)-butan-2-ol.”