Account for the following:
i) Aniline is a weaker base than methylamine.
ii) Aryl cyanides cannot be formed by the reaction of aryl halides with sodium cyanide.
i) Aniline is a weaker base than methylamine.
ii) Aryl cyanides cannot be formed by the reaction of aryl halides with sodium cyanide.
Solution
(i) In aniline the nitrogen lone pair conjugates with the ring, so it is less available and the anilinium ion is destabilised; methylamine's +I group does the opposite.
(ii) In ArX the lone pair of X conjugates with the ring, giving C–X double-bond character; nucleophilic substitution on the sp carbon is strongly resisted, so CN cannot displace the halide (aryl cyanides are made via diazonium/CuCN instead).
(ii) In ArX the lone pair of X conjugates with the ring, giving C–X double-bond character; nucleophilic substitution on the sp carbon is strongly resisted, so CN cannot displace the halide (aryl cyanides are made via diazonium/CuCN instead).
CBSE Class 12 Board · 2000 · All India Compartment · Subjective