A hydrocarbon of molecular mass 72 g `mol^(-1)` gives a single monochloro derivative and two dichloro derivatives on photo chlorination. Give the structure of the hydrocarbon.

Explanation

Molecular mass of hydrocarbon = 72
If it is a saturated hydrocarbon (alkane) then its molecular formula is `C_nH_(2n + 2)`
`:. 12 n + (2n + 2) xx 1 = 72 or 14n = 70 or n = 5` ?
Thus, the molecular formula of hydrocarbon is `C_5H_12`
Since on photochlorination, it gives a single monochlorination product, therfore, all the twelve hydrogens in this hydrocarbon are equivalent. Thus, the hydrocarbon must be neopentane or 2,2-dimethylpropane. It is gives one monochloro derivative and two dichloroderivatives as shown below: