One per cent composition of an organic compound A is, carbon : $85.71 \%$ and hydrogen $14.29 \%$. Its vapour density is 14 . Consider the following reaction sequence
Identify C.

• A

  
• Correct answer
  B

  $\mathrm{HO}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CO}_{2} \mathrm{H}$
• C

  $\mathrm{HO}-\mathrm{CH}_{2}-\mathrm{CO}_{2} \mathrm{H}$
• D

  $\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CO}_{2} \mathrm{H}$

Solution

$\mathrm{C}=85.71 \%=\frac{85.71}{12}=7.14 ; \frac{7.14}{7.14}=1$ $\mathrm{H}=14.29 \%=\frac{14.29}{1}=14.29, \frac{14.29}{7.14}=2$ $\therefore$ Empirical formula $=\mathrm{CH}_{2}$ and, empirical formulaweight $=12+2=14$ Nowsincemolecular formula weight $=2 \times$ vapour density $$ =2 \times 14=28 $$ $\therefore n=\frac{28}{14}=2$ $\therefore$ Molecular formula $=\left(\mathrm{CH}_{2}\right)_{2}=\mathrm{C}_{2} \mathrm{H}_{4}$

Hence, the correct answer is option: 'B'.