The transformation of (X) benzene with Br and CH₃ substituents to (Y) benzene with CH₂COOH requires:
First, NaOEt causes elimination of HBr to form an alkene intermediate.
Second, B₂H₆/H₂O₂ performs hydroboration-oxidation, adding hydroxyl group in anti-Markovnikov fashion to yield a primary alcohol.
Third, Jones reagent oxidizes the primary alcohol to carboxylic acid.
The sequence NaOEt → B₂H₆/H₂O₂ → Jones reagent produces the desired carboxylic acid product.
