Chemistry - STRUCTURAL ISOMERISM Question with Solution | TestHub

Question Explanation:

The question asks to determine how many of the given compounds are capable of exhibiting

tautomerism.

Concept:

This question is based on the structural requirements for tautomerism (mainly keto–enol or nitro–aci

tautomerism).

Solution:

For tautomerism to occur, the molecule must satisfy:

Presence of at least one α-hydrogen on an sp carbon adjacent to an electron-withdrawing group

such as –C=O, –NO₂ , –CN, etc.

The structure must allow proton migration and double-bond shift.

In conjugated (α,β-unsaturated) systems, γ-hydrogens may also participate through vinylogy.

Compounds lacking α-hydrogen adjacent to the functional group do not show tautomerism.

Among the eight given compounds, seven ((a), (c), (d), (f), (g), (h) & (j)) possess at least one acidic α-

hydrogen (or equivalent hydrogen in a conjugated system) that enables tautomerism.

The circled carbon atoms contain enolisable (α- or γ-) hydrogen atoms, which can undergo tautomerism under suitable acidic or basic conditions.

Rest other compounds lack the necessary α-hydrogen and therefore cannot undergo tautomerism.