Question

Which among the given molecules can exhibit tautomerism?

• A. III only
• B. Both I and III
• C. Both I and II
• D. Both II and III

Answer 1

The Correct Option is A

Tautomerism refers to a phenomenon where isomers (called tautomers) rapidly interconvert through the migration of a proton (H⁺) or a hydrogen atom within a molecule. This usually happens between two structural forms that differ only in the position of a hydrogen atom and a double bond.

α-Hydrogen: In organic chemistry, α-hydrogen refers to the hydrogen atoms attached to the carbon adjacent to a functional group (often a carbonyl group). These hydrogens are typically involved in reactions like tautomerism.

Bridge Carbon: A bridge carbon is part of a cyclic structure in some molecules where it connects two parts of a ring.

α-Hydrogen at a bridge carbon does not participate in tautomerism because it is less likely to form a structure where the hydrogen can migrate in the tautomeric transition.

Only (III) exhibits tautomerism, indicating that in this specific case, the other molecules (presumably labeled (I) and (II)) do not undergo tautomerism due to the lack of α-hydrogens or because they are involved in a more rigid structure.