Benzophenone is even more hindered than acetophenone:$$(C_6H_5)_2C=O$$

Two effects make $HSO_3^-$ addition difficult:

1. Very high steric hindrance
   The carbonyl carbon is surrounded by two phenyl groups, so $HSO_3^-$ cannot easily attack it.
2. Resonance/conjugation
   The carbonyl group is conjugated with both benzene rings, reducing the electrophilic character of the carbonyl carbon.

Reactivity comparison

$$\boxed{\text{Aldehydes} > \text{acetophenone} > \text{benzophenone}}$$

So for the NaHSO₃ addition test:

• Aldehydes → generally react readily ✅
• Acetophenone → poor/slow reaction
• Benzophenone → generally does not react under usual conditions ❌

Key JEE/NEET fact: Benzophenone is a classic example of a ketone that does not form the usual sodium bisulfite addition compound readily because of steric hindrance + resonance stabilization.