Halogenoalkanes are classified as primary, secondary or tertiary. The classification depends on how many alkyl groups are attached to the carbon atom that is bonded to the halogen.In a primary halogenoalkane that carbon is attached to one other carbon atom, for example 1-bromobutane. Halomethanes such as chloromethane are also grouped as primary.In a secondary halogenoalkane the carbon is attached to two other carbon atoms, for example 2-bromobutane.In a tertiary halogenoalkane the carbon is attached to three other carbon atoms, for example 2-bromo-2-methylpropane.
The classification helps to predict which reaction happens with hydroxide ions, since tertiary halogenoalkanes are more likely to undergo elimination.
The classification helps to predict which reaction happens with hydroxide ions, since tertiary halogenoalkanes are more likely to undergo elimination.