question_answer 91)

    Note : In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices. (a) Both assertion and reason are wrong. (b) Both assertion and reason are correct statements but reason is not correct explanation of assertion. (c) Assertion is correct statement but reason is wrong statement. (d) Both assertion and reason are correct statements and reason is correct explanation of assertion. (e) Assertion is wrong statement but reason is correct statement.   Assertion: Acylation of amines gives a monosubstituted product whereas alkylation of amines gives polysubstituted product.   Reason: Acyl group sterically hinders the approach of further acyl groups. (a) Both assertion and reason are wrong. (b) Both assertion and reason are correct statements but reason is not correct explanation of assertion. (c) Assertion is correct statement but reason is wrong statement. (d) Both assertion and reason are correct statements and reason is correct explanation of assertion. (e) Assertion is wrong statement but reason is correct statement.

Answer:

                    (c) Correct reason. Due to delocalization of the lone pair of electrons of the N-atom over the carbonyl group in the acyl derivative, the electron density on the N-atom decreases to such an extent that it does not act as a nucleophile at all and hence does not react with another molecule of the acylating agent.