If one or more hydrogen atom is replaced in hydrocarbon by equivalent number of halogen, the compounds obtained are called halogen derivatives of hydrocarbons.
Halogen derivatives of hydrocarbons are further classified as aliphatic halogen compounds and aromatic halogen compounds.
Aliphatic halogen compounds are obtained by replacing one or more hydrogen of aliphatic hydrocarbons (alkanes, alkenes and alkynes). Aliphatic halogen compounds are further classified as haloalkanes, haloalkenes and haloalkynes.
Halogen derivatives of arenes are called aromatic halogen compounds.
Aromatic halogen compounds are further classified as nuclear halogen derivatives and side chain halogen derivatives.
When hydrogen atom directly attached to an aromatic ring is replaced by halogen atom, compound obtained is called nuclear halogen derivative of arene or haloarene or aryl halide.
When a hydrogen atom present in a side chain attached to an aromatic ring is replaced by halogen atom, the derivative obtained is called side chain derivative. The side chain halogen derivatives are regarded as the aryl derivatives of haloalkane.