Q.

Which of the following has highly acidic hydrogen                    [2024]

 

1  
2  
3  
4  

Ans.

(2)

Acidic strength of an acid stability of conjugate base.

Conjugate base of (2) is stabilised by −M effect of two carbonyl groups whereas, in all other options conjugate base gets −M stability of only one carbonyl group. Thus (2) has most acidic hydrogen.