Question

Which of the following compounds cannot be acetylated?
(A) $C{{H}_{3}}N{{H}_{2}}$
(B) ${{(C{{H}_{3}})}_{2}}NH$
(C) ${{(C{{H}_{3}})}_{3}}N$
(D) None of these

Answer 1

Hint: The chemical process of adding an acetyl functional group to a chemical molecule is known as acetylation. When treated with acid chloride, anhydride, or esters, aliphatic and aromatic primary and secondary amines undergo acetylation reactions via nucleophilic substitution. This process occurs in the presence of a strong base like pyridine. When an amine reacts with acid chloride, it releases $HCl$ . This $HCl$ shifts the equilibrium to the right hand side of the reaction.

Complete Step by Step Solution:
For compounds to get acetylated, it is necessary to have $\alpha $ – hydrogen. In this case, methyl amine ($C{{H}_{3}}N{{H}_{2}}$ ), a primary amine, has two -hydrogens, while dimethyl amine (${{(C{{H}_{3}})}_{2}}NH$) , a secondary amine, has one. So, these compounds can be acetylated easily with acid chloride, anhydride, or esters. However, because there is no $\alpha $ -hydrogen attached to $N$ in trimethylamine (${{(C{{H}_{3}})}_{3}}N$ ), a tertiary amine, it cannot be acetylated.
Correct option: (C) ${{(C{{H}_{3}})}_{3}}N$.

Additional Information: The process of amines reacting with benzoyl chloride is known as benzoylation. Deacetylation, which means removing an acetyl group from a chemical compound, can be considered the opposite reaction to acetylation.

Note: The hydrogen attached to nitrogen is analysed and not with carbon as the hydrogen attached to nitrogen gets released in the form of $HCl$ , which shifts the equilibrium to the right hand side of the reaction. So, there should be at least one hydrogen attached to nitrogen in an amine to undergo acetylation.