Question

The correct order of acidity for the following compounds is:

• A. II < IV < III < I
• B. II < III < I < IV
• C. II < III < IV < I
• D. III < II < I < IV

Answer 1

The correct option is B II < III < I < IV

Acidity will be most when the conjugate base is most stabilised.

Carboxylic acid is more acidic than phenol.
For nitro substituted phenol, $N{O}_2$ when present at para position will show maximum acidity due to -R effect while at meta position it shows only -I effect. Since -R effect is more pronounced over -I therefore (I) will be more acidic than (III).
Methyl group destabilises the conjugate base through +I effect and hence (II) will be least acidic.