Question

Arrange the above compounds in decreasing order of their acidic strength:

• A. $\left(I\right)>\left(II\right)>\left(III\right)>\left(IV\right)$
• B. $\left(II\right)>\left(I\right)>\left(IV\right)>\left(III\right)$
• C. $\left(III\right)>\left(IV\right)>\left(II\right)>\left(I\right)$
• D. $\left(III\right)>\left(II\right)>\left(I\right)>\left(IV\right)$

Answer 1

The correct option is D $\left(III\right)>\left(II\right)>\left(I\right)>\left(IV\right)$

Electron withdrawing groups like $-N{O}_2$, increases the acidity of carboxylic acids by stabilizing the conjugate base through resonance effects, whereas, electron-donating groups decrease the acidity of carboxylic acids by destabilizing the conjugate base through resonance.

Electronic effect will decide the acidic strength in different ortho substituted benzoic acids. More is the strength of electron withdrawing group attached in the ring, more is the acidic strength.
The order of electron withdrawing groups is: $-N{O}_2>-Cl>-C{H}_3>-OC{H}_3$.

So, option D is correct.