Browse Questions

Which of the following organic compound shows Keto–enol tautomerism?

(a) Benzophenone

(b) Benzaldehyde

(c) Di-tert-butyl ketone

(d) none of these

Toolbox:
• Ketanol tautomerism refers to a chemical equilibrium between a keto form (a ketone or an aldehyde) and an enol. The enol and keto forms are said to be tatutomers of each other. The interconversion of the two forms involved the movements of a proton and the shifting of bonding electrons.
• A compound containing a carbonyl group $(C=0)$ is normally in rapid equilibrium with an enol tautomer, which contains a pair of doubly bonded carbon atoms adjacent to a hydroxyl $(-OH)$ group, $C=C-OH$ For a carbonyl compound to exhibit tautomerism, the essential condition is that, it must have at least one $\alpha -H$ atom.
• Generally , the keto form is more stable than the enol form due to the greater strength of the carbon- oxygen $\pi$ bond as compared - carbon $\pi$ bond.
All the compounds do not have $\alpha$ - hydrogens and hence do not show tautomerism.
Hence d is the correct answer.
edited Mar 25, 2014