Classification:

Haloalkanes can be classified into three groups:

Primary halogenoalkanes

In a primary (1°) halogenoalkane, the carbon which carries the halogen atom is only attached to one other alkyl group.

Some examples of primary halogenoalkanes include:

Notice that it doesn't matter how complicated the attached alkyl group is. In each case there is only one linkage from the CH₂ group holding the halogen to an alkyl group.

There is an exception to this. CH₃Br and the other methyl halides are often counted as primary halogenoalkanes even though there are no alkyl groups attached to the carbon with the halogen on it.

Secondary halogenoalkanes

In a secondary (2°) halogenoalkane, the carbon with the halogen attached is joined directly to two other alkyl groups, which may be the same or different.

Examples:

Tertiary halogenoalkanes

In a tertiary (3°) halogenoalkane, the carbon atom holding the halogen is attached directly to three alkyl groups, which may be any combination of same or different.

Examples: