Chemistry - CHEMICAL BONDING Question with Solution | TestHub

Structure (I) is the keto form, where the carbonyl groups are separated by a methylene ($-$CH₂$-$) group. It lacks a hydrogen atom bonded to a highly electronegative atom (like O, N, or F) required for hydrogen bonding.

Structure (II) is the enol form. It contains a hydroxyl ($-$OH) group in close proximity to a carbonyl oxygen (C$=$O), allowing for the formation of a stable six-membered ring via intramolecular hydrogen bonding.

Therefore, only isomer (II) exhibits hydrogen bonding.