What do you mean by dehalogenation reaction?

Explanation

a) Hydrocarbon having molecular formula `C_5 H_(10)` can be either a cycloalkane or an alkene b) As hydrocarbon does not react with `Cl_2` in dark, it cannot be alkene, so it must be cycloalkane. c) As cycloalkane react with `Cl_2` in presence of bright light to give monochloro compound, prove all ten hydrogen atome of cycloalkanes must be equalent. So cycloalkane is cyclopentans.
No reaction