Question

A hydrocarbon C₅H₁₀ does not react with chlorine in the 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 CnH₂n. Therefore, it may either be an alkene or a cycloalkane. Since hydrocarbon does not react with chlorine in the dark, it cannot be an alkene. 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 monochloride mixture is formed, the hydrocarbon must contain all equivalent H-atoms. Also, as all H−atoms of a cycloalkane are identical, the hydrocarbon must be a cycloalkane. Hence, the said compound is cyclopentane. 

The reactions involved in the question are: