Question

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.

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 correct statements but reason is not the correct explanation of assertion.
• B. Assertion is wrong statement but reason is correct statement.
• C. Both assertion and reason are wrong.
• D. Both assertion and reason are correct statements and reason is correct explanation of assertion.
• E. Assertion is correct statement but reason is wrong statement.

Answer 1

The correct option is E Assertion is correct statement but reason is wrong statement.

Assertion:

Acylation or alkylation of amines is a nucleophilic substitution reaction in which amines act as a nucleophile.

Alkylation of amines gives polysubstituted products because nucleophilicity of amines increases with increase in the number of the electron releasing group (alkyl groups) on amine. So, further reaction of alkyl halide for alkylation takes place with more substituted amines.

$R—N{H}_2+R—X\to R—NH—R+HX$
1amine 2amine More nucleophilic than
1 amine

Alkylation gives polysubstituted products because increase in alkyl group (showing +I effect) increases the nucleophilicity of nitrogen atom of the amine.

In an acylated amine, lone pair of nitrogen is in conjugation with the adjacent carbonyl group. hence electron density on the $N-$atom is decreased.

In the resonating structure of acylated amine, the negative charge on more electronegative oxygen atom is highly stabilized.

Hence acylated amine is less nucleophilic than primary amines.

Resonance in acylated amines
So, acylation of amines gives a monosubstituted product due to reduced nucleophilicity of nitrogen atom, whereas alkylation of amines gives polysubstituted product.

Therefore, assertion is correct.

Reason:

Acylation of amines gives a monosubstituted product, because the conjugation of lone pair of nitrogen with carbonyl group reduces its nucleophilicity.

Hence acylated amine is less nucleophilic than primary amines.

So, the reason statement is false.

Therefore, the assertion is the correct statement, but the reason is the wrong statement.

Hence option (C) is correct.