Animated Solution for Chemistry - Organic Chemistry: Given below are two statements. Statement I Aniline is less basic than acetamide. Statement II In aniline, the lone pair of electrons on nitrogen atom is delocalised over benzene ring due to resonance and hence less available to a proton. Choose the most appropriate option :

The battle of basicity between aromatic amines and amides is a classic concept in organic chemistry that tests your understanding of resonance and electronegativity. In this problem, we are presented with two statements comparing the basicity of aniline and acetamide, and we need to determine their validity.

Let's start by examining Statement II, which focuses on aniline ($C_6{H}_{5}N{H}_2$). The basicity of any amine is fundamentally determined by the availability of the lone pair of electrons on the nitrogen atom. The more available this lone pair is to accept an incoming proton ($H^{+}$), the stronger the base.

In aniline, the nitrogen atom is directly attached to a benzene ring. This structural arrangement allows the lone pair on the nitrogen to participate in resonance with the delocalized $\pi$-electron system of the aromatic ring. Because of this delocalization, the lone pair spends a significant amount of time distributed inside the ring rather than localized on the nitrogen atom.

Consequently, the lone pair is less available to bond with a proton. This resonance effect makes aniline a significantly weaker base compared to typical aliphatic amines. Therefore, Statement II is absolutely true.

Now, let's evaluate Statement I, which claims that aniline is less basic than acetamide ($C{H}_{3}CON{H}_2$). To verify this, we must look at the structure of acetamide.

In acetamide, the nitrogen atom is adjacent to a carbonyl group ($C=O$). The lone pair on the nitrogen is in direct conjugation with the $\pi$-bond of the carbonyl group. Oxygen is a highly electronegative element—much more so than the $s{p}^2$ hybridized carbon atoms in a benzene ring.

Because of oxygen's strong electron-withdrawing nature, it pulls the electron density towards itself very effectively. The resonance in acetamide involves the lone pair shifting towards the oxygen, creating a resonance structure where the oxygen bears a negative charge and the nitrogen bears a positive charge.

This strong delocalization means that the lone pair in acetamide is practically unavailable for protonation. In fact, acetamide is so weakly basic that it is considered almost neutral in aqueous solutions.

When we compare the two, aniline is a weak base due to resonance with the benzene ring, but acetamide is almost entirely non-basic due to the powerful electron-withdrawing effect of the highly electronegative carbonyl oxygen.

Therefore, aniline is actually more basic than acetamide. Statement I, which states that aniline is less basic, is completely false.

Final Conclusion: Statement I is false, but Statement II is true.