Question

Identify the compound that exhibits tautomerism?

• A. 2-Butene
• B. Lactic acid
• C. 2-Pentanone
• D. Phenol

Answer 1

The correct option is C

2-Pentanone

Lets just first draw the structure of each molecule.

Lactic acid -- CH3-CH(OH)-COOH

One of the necessary conditions for tautumerism is the presence of $\alpha$-hydrogen

$\to$ $\alpha$-hydrogen is present on $\alpha$- carbon

Therefore these conditions are possible only in option (C)

$\underset{Ketoform}{C{H}_3-\stackrel{\underset{||}{O}}{C}-C{H}_2-C{H}_2-C{H}_3}\leftrightharpoons \underset{Enolform}{C{H}_3-\stackrel{\underset{|}{OH}}{C}=CHC{H}_{2}C{H}_3}$