Question

Consider the following pairs of compounds

Of these pairs

• A. both X and Y are resonance forms
• B. both X and Y are tautomeric forms
• C. X is a resonance pair, while Y is a pair of tautomers
• D. X is a pair of tautomers; while Y is a resonance pair

Answer 1

Answer: (C)

In '$X$' pair of compounds, de-localisation of electrons occurs without the change in the relative position of bonded atoms (or nuclei). Hence, $X$ is a resonance pair.
In $Y$ pair of compounds, shifting of proton $\left(H^{+}\right)$ occurs from $N$ atom to $O$ atom. Hence, '$Y$' is a pair of tautomers.