Question

A hydrocarbon C₅H₁₀ does not react with chlorine in dark but gives a single monochloro compound C₅H₉Cl in bright sunlight. Identify the hydrocarbon.

Answer 1

A hydrocarbon with the molecular formula C₅H₁₀ belongs to the group with a general molecular formula of C_nH_2n. Therefore, it may either be an alkene or a cycloalkane.

Since hydrocarbons do not react with chlorine in the dark, they cannot be alkenes. Thus, it should be a cycloalkane.

Further, the hydrocarbon gives a single monochloro compound, C₅H₉Cl, by reacting with chlorine in bright sunlight. Since a single monochloro compound is formed, the hydrocarbon must contain H-atoms that are all equivalent. Also, as all H-atoms of a cycloalkane are equivalent, the hydrocarbon must be a cycloalkane. Hence, the said compound is cyclopentane. The reactions involved are