Question

A hydrocarbon (A) was found to have vapour density 36. It forms only single mono chlorosubstitution product.Suggest (A).

• A. 2,2-dimethylpropane
• B. n-pentane
• C. isobutane
• D. None of these

Answer 1

Answer: (A)

2,2-dimethylpropane

$Molecularwt.=2\times vapourdensity=2\times 36=72$

For an alkane, compound formula will be $C_n{H}_{2n+2}$

$Molecularwt.=12n+(2n+2)\times 1=14n+2$

$⟹14n+2=72⟹n=5$

Compound formula is $C_5{H}_{12}$

Since only one type of monochloro product is formed after monochlorination, only one type of hydrogen must be present. 2,2-dimethyl propane has only primary hydrogens.

Hence, A is the correct option.