question_answer

Which compound in the following pairs will react faster in \[{{S}_{{{N}^{2}}}}\] reaction? (a) \[C{{H}_{3}}Br\]or\[C{{H}_{3}}I\] (b) \[{{(C{{H}_{3}})}_{3}}Br\] or \[C{{H}_{3}}Br\] (c) \[C{{H}_{2}}=CHBr\]or \[C{{H}_{2}}=CH-C{{H}_{2}}Br\].

Answer:

                (a) \[C{{H}_{3}}I\]will react faster since \[C-I\] bond can cleave more easily as compared to C?Br bond. (b) \[C{{H}_{3}}Br\]will react faster because less steric hindrance as compared to \[{{(C{{H}_{3}})}_{3}}CBr\]. (c) \[C{{H}_{2}}CH-C{{H}_{2}}Br\] will react faster because in \[C{{H}_{2}}=CHBr\] molecule, \[C-Br\] bond has a partial double bond character due to resonance and its cleavage is more difficult as compared to \[C{{H}_{2}}=CH-C{{H}_{2}}-Br\] in which the bond does not have partial double bond character.