Alkyl halides (halogen atom is attached to sp3 hybridised carbon atom) and aryl halides (halogen atom is attached to sp2 hybridised carbon atom) both are classified as mono-, di-, tri- or polyhalogen derivatives depending on the number of halogen atoms present in their structure.
a) Alkyl halides - General formula is Cn H2n+1X
• Classified as primary (1°), secondary (2°) or tertiary (3°) depending on if the halogen is attached to a primary, secondary or tertiary carbon atom.
`
• can also be classified as geminal or vicinal dihalides deeanding on whether the two halogen atoms are present on the same carbon atom (geminal) or on adjacent carbons (vicinal)
b) Allylic halides - halogen atom is attached to that sp3− hybridised carbon atom which is next to a carbon-carbon double bond i.e. to an allylic carbon atom
c) Benzylic halides - halogen atom is attached to that sp3 hybridised carbon atom which is bonded to an aromatic ring
d) Vinyl halide - halogen atoms is attached to an sp2 hybridised carbon atom of a double bond.
e) Aryl halide - halogen atom is directly attached to the sp2 hybridised carbon atom of an aromatic ring
