Final answer:
The major product of HBr addition to the described benzene with a propenyl group is benzene with a 2-bromopropane group, following Markovnikov's rule.(CH3-CHBr-CH2-).
Step-by-step explanation:
The major product obtained from the addition of HBr to the compound described would be the result of a Markovnikov addition across the alkene portion of the molecule.
The compound mentioned seems to be a benzene ring with an attached propenyl group (CH2=CH-CH2-). When HBr is added to an alkene, the hydrogen atom attaches to the carbon with the most hydrogen atoms already present, and the bromine attaches to the other carbon, following Markovnikov's rule.
Therefore, the major product would be the benzene ring with an attached 2-bromopropane group (CH3-CHBr-CH2-).