The isomers are:
CH3CH2CH2CH2-Br most responsive, recause there is slightest gathering around the essential carbon iota for the nucleophile to assault.
(CH3)2CHCH2-Br second generally responsive.
.......Br
.......|
CH3CHCH2CH3 thid generally responsive.
(CH3)3C-Br slightest receptive. It is, be that as it may, energetically responsive in a Sn1 response. This is on the grounds that (CH3)3C+ is an exceptionally stable carbonium particle.