Question

$C{H}_3-C{H}_2-COOH\underset{\text{Red P}}{\overset{C{l}_2}{\to }}A\underset{H_{3}O}{\overset{NaCN}{\to }}B\stackrel{\Delta }{\to }C,$
'C' is_______.

• A. 2-methylpropan dioic acid
• B. Propanoic acid
• C. Lactic acid
• D. Hexanoic acid

Answer 1

The correct option is B Propanoic acid

Carboxylic acid with $\alpha$-hydrogen on reacting with halogens $\left(X_2\right)$ in presence of red phosphorus gives $\alpha$-Halo-​carboxylic acid.
$\alpha$-Halo-​carboxylic acid on reacting with $NaCN$ undergoes nucleophilic substitution reaction to give $\alpha$-cyano-​carboxylic acid. When the formed product is hydrolysed, nitrile is converted to carboxylic acid and gives 1, 3 dicarboxylic acid formation.
1, 3-dicarboxylic acid on heating undergoes decarboxylation to give respective product.


Decarboxylation of 1, 3 dicarboxylic acid,

Hence, option (b) is correct.