Question

The most acidic compound out of the following is :

• A. A
• B. B
• C. C
• D. D

Answer 1

The correct option is B B

The acidity of the compounds depends on stability of conjugate base formed .
The conjugate bases formed are :

At, ortho and para position, predominant effect of $-N{O}_2$is $-M$ effect,whereas at meta position , it shows $-I$ effect.
Also, $-C{H}_3$ when attached at para position shows predominantly $+H$ effect . $+H$ effect destabilizes the negative charge, whereas the conjugate base is stabilized by $-M$ and $-I$ effect of $-N{O}_2$ group.
More the nitro groups attached , more is the stability of conjugate base.
So, B is the most stable conjugate base formed, and hence the most acidic.