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

The hydrocarbon having molecular mass of 72 g `mol^(-1)` must be `C_(5)H_(12)`. Since on photochlorination, it gives a single monochloro derivative, therefore, all the twelve hydrogens in this hydrocarbon are equivalent. Thus, the hydrocarbon must be neopentane or 2,2-dimethylpropane, it forms only one monochloro derivative and two dichloro derivatives as shown below:
`underset("2,2-Dimethylpropane (All the 12 H's are equivalent)")(CH_(3)-underset(CH_(3))underset(|)overset(CH_(3))overset(|)(C)-CH_(3))" "underset("1-Chloro-2,2-dimethylpropane (Monochloro derivative)")(CH_(3)-underset(CH_(3))underset(|)overset(CH_(3))overset(|)(C)-CH_(2)Cl)" "underset("1,3-Dichloro-2,2-dimethylpropane (Dichloro derivative)")(CH_(3)-underset(CH_(3))underset(|)overset(CH_(2)Cl)overset(|)(C)-CH_(2)Cl)" "underset("1,1-Dichloro-2,2-dimethylpropane (Dichloro derivative)")(CH_(3)-underset(CH_(3))underset(|)overset(CH_(3))overset(|)(C)-CHCl_(2))`.