Question

8. Which one of the following compound is most acidic? ҮОН od Br IV

Answer 1

After H is removed, the conjugate base is formed.
We need to see the stability of the conjugate base.

The more stable the conjugate base, stronger will be the acid.

The part which is changing in all the molecules is:
In II, we have F which contributes to -I effect to stabilise the negative charge on O

In III, we have I which contributes to -I effect to stabilise the negative charge on O

In IV, we have Br which contributes to -I effect to stabilise the negative charge on O

Electronegativity is most for F and hence -I effect will be maximum for II.

So, II forms most stable conjugate base.
So, II is strongest acid

Answer: B. II