Formation of a stable hydrate

Question: Which of the following does not form a stable hydrate?

I think they mean nucleophilic addition of water. For compound (C), on reaction with water, the product formed is

The product has lesser bond angle strain than the reactant. Hence, the compound formed is stable. This is because $\ce{sp^2}$ hybridised carbonyl carbon requires $120^{\circ}$ but only gets $60^{\circ}$ in cyclopropanone. But converting it into a diol makes the angle $109^{\circ}$ which reduces strain to a large extent. In fact, cyclobutanone is also reactive to water.

For (B) however, there is not much change in the bond angle strain. The initial angle is already close to the required angle.

What can I say about (A) and (D)?

• D forms stable hydrate due to intra molecular H-Bonding Dec 26 '15 at 2:14
• So the answer is B. Its correct. Dec 26 '15 at 4:25

If water is present, poly-vicinal carbonyl compounds usually exist as hydrates. Drawing the resonance structure of a carbonyl compound we see the the $\ce{C=O}$ bond is highly polarized with the carbon terminus being the positive end. If we have several carbonyls adjacent to one another, then each carbonyl has this same polarization and an electrostatic destabilization results. This is particularly true for the central carbon since there is a partial positive charge on each of the carbons attached to it.