Given, Which of the given compounds can exhibit tautomerism?

Given,

Which of the given compounds can exhibit tautomerism?

  1. I and II
  2. I and III
  3. II and III
  4. I, II and III

Solution

All compounds show tautomerism.



Of many types of tauomerism possible, keto-enol tauomerism is the most commonly encountered one.

It is possible in presence of α-C (wrt the carbonyl group), which is the conjugate C-H bond having sp3 hybridization.

Usually it is the α-C of the carbonyl group constituting a triad system, however it could also sometimes be the γ-C, if there is a C=C present on α-β carbons, constituting a quinquad system.

Compound (I) & (II) are have tautomerism in a triad system, while (III) involves a quinquad system as shown here:

Asked in: NEET 2015 (Phase 1)

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