Answer:
1-bromobutane
Explanation:
The reaction of butane with aqueous HBr at reflux is an SN2 reaction. The reaction passes through a single transition state in which the bond between carbon and the leaving group as well as the bond between carbon and the incoming nucleophile are being broken and formed simultaneously. It is a synchronous reaction.
The nuclephile attacks from the backside while the leaving group departs. This leads to inversion of configuration of the product.
