JEE Chemistry 2025 Question with Solution

Given: $1.0 \, \text{g}$ of the most basic compound is treated with HCl. The compounds shown include p-nitroaniline, benzylamine, acetanilide-type amide, and aniline.

Find: Mass of HCl consumed in mg.

From the given compounds, benzylamine is the most basic compound. The lone pair on nitrogen is not directly conjugated with the benzene ring, so it is more available for protonation than in aniline or the other substituted aromatic nitrogen compounds.

The reaction with HCl is in a $1:1$ molar ratio:

Molar mass of benzylamine:

Moles of benzylamine in $1.0 \, \text{g}$:

Therefore, moles of HCl consumed are also:

Mass of HCl consumed:

the solution states 1260 mg, but that does not follow from the structures shown and the $1:1$ stoichiometry with HCl. Using the displayed compounds, the defensible numerical value is $341$.

Aromatic amines such as aniline have the nitrogen lone pair delocalized into the benzene ring, which reduces basicity. In p-nitroaniline, the nitro group further withdraws electron density, making it even less basic. In the amide structure, the lone pair is strongly delocalized toward the carbonyl group, so it is the least basic among these.

In benzylamine, the nitrogen is attached to the ring through a $\text{CH}_2$ group, so its lone pair is not conjugated with the benzene ring. Hence it is the most basic compound among the given structures.