An isomer X of molecular formula C ₈ H ₉ Br is found to be optically active. It is reacted with magnesium in dry ether, followed by treatment with CO ₂ and subsequent acidic hydrolysis to yield compound Y. Compound Y is then treated with Br ₂ in the presence of red phosphorus to give compound Z as the major product. The structure of compound Z is:

Step-by-step solution

The molecular formula of X is C ₈ H ₉ Br . Since X is optically active, it must possess a chiral center. The only isomer of C ₈ H ₉ Br with a chiral center is 1-bromoethylbenzene, C ₆ H ₅- CH ( Br )- CH ₃ . Reaction of X with Mg in dry ether forms the Grignard reagent, which upon reaction with CO ₂ followed by acidic hydrolysis yields the carboxylic acid Y. Thus, Y is 2-phenylpropanoic acid, C ₆ H ₅- CH ( CH ₃)- COOH . Treatment of Y with Br ₂ and red phosphorus is the Hell-Volhard-Zelinsky (HVZ) reaction, which re