A statement of Assertion is given followed by a corresponding statement of Reason (R). Choose the correct answer from the given options.

Assertion: Acylation of amines gives a monosubstituted product whereas alkylation of amines gives polysubstituted product.

Reason: Acyl group strically hinders the approach of further acyl groups.

Assertion is correct but reason is incorrect

Assertion: Acylation of amines gives a monosubstituted product whereas alkylation of amines gives polysubstituted product.

This statement is generally true. Acylation reactions typically result in the formation of a single amide bond between the acyl group \((RCO^-)\) and the amine group \((NH_2)\). The steric hindrance (bulkiness) of the newly attached acyl group makes it less likely for another acyl group to react with the remaining amine nitrogen.

Reason: Acyl group strictly hinders the approach of further acyl groups.

This statement is not entirely accurate. While steric hindrance does play a role, it's not the only factor. Here's a more nuanced explanation:

Steric hindrance: The attached acyl group can create a physical barrier that hinders the approach of another acyl group to the remaining amine nitrogen. This effect is more pronounced with bulkier acyl groups.

Basicity change: After the initial acylation, the remaining amine nitrogen becomes less basic due to the electron-withdrawing nature of the acyl group. This decreased basicity makes it less reactive towards further acylation.

Reaction conditions: Depending on the specific reaction conditions (temperature, concentration, etc.), it might be possible to achieve some degree of diacylation (attachment of two acyl groups) under certain circumstances. However, this is less common compared to alkylation.

Alkylation of amines:

Alkylation reactions, on the other hand, can sometimes lead to polysubstituted products (attachment of multiple alkyl groups) depending on the reaction conditions and the structure of the reactants. Primary amines (one alkyl group attached to the nitrogen) are more susceptible to dialkylation or trialkylation compared to secondary amines (two alkyl groups) or tertiary amines (three alkyl groups) due to the higher availability of the amine nitrogen for further reaction.

In conclusion, while the assertion about acylation is generally correct, the reason focuses solely on steric hindrance. The basicity change of the amine and the reaction conditions also contribute to the observed outcome. Alkylation reactions can potentially lead to polysubstituted products depending on the circumstances.