Question

With respect to the compounds $I-V$, choose the correct statement(s).

• A. The acidity of compound $I$ is due to delocalization in the conjugate base.
• B. The conjugate base of compound $IV$ is aromatic.
• C. Compound $II$ becomes more acidic, when it has a $-N{O}_2$ substituent.
• D. The acidity of compounds follows the order $I>IV>V>II>III$.

Answer 1

Answer: (A), (B), (C)

Compound $II$ becomes more acidic, when it has a $-N{O}_2$ substituent.

a) is a conjugate base of compound $I$, which is stabilized by delocalization or resonance.

b) Conjugate base of $IV$ is



which is an aromatic anion.

c) $-N{O}_2$ group is a strong electron-withdrawing group, which increases the acidic strength of compound $II$.

d) The order of acidic strength on the basis of $pKa$ value is: $IV>V>I>II>III$.