Isobutyl bromide may be obtained from isobutylene and HBr in the presence of

Peroxide

The correct answer is option 3. peroxide.

Isobutyl bromide can be obtained from isobutylene and HBr in the presence of a peroxide, such as benzoyl peroxide. The peroxide acts as a free radical initiator, which causes the HBr to add to the isobutylene in an anti-Markovnikov fashion.

The other options are incorrect. Option (1) hydroquinone, is a reducing agent and will not react with isobutylene or HBr. Option (2) diphenylamine, is a free radical scavenger and will inhibit the reaction between isobutylene and HBr.