Question

Which of the following gives unsaturated acid on heating?

• A. $C{H}_3\underset{OH}{\underset{|}{CH}}COOH$
• B. $\underset{OH}{\underset{|}{C}}{H}_{2}C{H}_{2}COOH$
• C. $C{H}_{3}C{H}_{2}C{H}_{2}COOH$
• D. All of these

Answer 1

The correct option is B $\underset{OH}{\underset{|}{C}}{H}_{2}C{H}_{2}COOH$

$\alpha$-Hydroxy acids on heating undergo intermolecular dehydration and forms lactides.
$\beta$-Hydroxy acid undergoes intramolecular dehydration and gives unsaturated acid on heating.