The correct order of the rate of the reaction for the following reaction with respect to nucleophiles is : CH3Br + Nu- CH3Nu + Br-
- ClO4- > CH3COO- > OH- > PhO-
- OH- > PhO- > CH3COO- > ClO4-
- CH3COO- > PhO- > OH- > ClO4-
- PhO- > OH- > CH3COO- > ClO4-
Answer
(2) OH- > PhO- > CH3COO- > ClO4-
Solution
CH3Br (a methyl halide) reacts by SN2; the rate depends on the strength of the nucleophile.
All four nucleophiles attack through oxygen, so nucleophilicity runs parallel to basicity.
Acid strength of conjugate acids: HClO4 > CH3COOH > C6H5OH > H2O
Basicity: OH- > PhO- > CH3COO- > ClO4-
The negative charge is localised on O in OH-, delocalised into the ring in PhO-, over two O atoms in CH3COO- and over four O atoms in ClO4-.
Rate: OH- > PhO- > CH3COO- > ClO4-
Answer: (2)