There are four isomeric haloalkanes with molecular formula C4H9Br
The primary bromides are 1-bromobutane,
CH3CH2CH2CH2Br, and 1-bromo-2-methylpropane,
(CH3)2CHCH2Br
The secondary bromide is 2-bromobutane,
CH3CH2CHBrCH3.
The tertiary bromide is 2-bromo-2-methylpropane,
(CH3)3CBr.