An aromatic hydrocarbon X having the molecular formula C ₉ H ₁₂ is heated with alkaline KMnO ₄ followed by acidification to yield a dicarboxylic acid Y. Compound Y undergoes electrophilic bromination with Br ₂ in the presence of FeBr ₃ to yield only a single monobrominated product. The number of benzylic hydrogen atoms in compound X is _______.

Step-by-step solution

(i) Oxidation of hydrocarbon X ( C ₉ H ₁₂ ) yields a dicarboxylic acid (Y). This indicates the presence of two alkyl side chains on the benzene ring. (ii) The remaining 3 carbon atoms (since the benzene ring accounts for 6) must be distributed as a methyl group ( - CH ₃ ) and an ethyl group ( - CH ₂ CH ₃ ). (iii) Compound Y is a benzenedicarboxylic acid. Since it yields only a single monobrominated product upon electrophilic aromatic substitution, all four available positions on its benzene ring must be equivalent