Benzene diazonium chloride on reaction with KCN in the presence of CuCN yields X. X on hydrolysis gives Y. Y can also be obtained from
Toulene by the action of Cl2/ FeCl3
Toulene by the oxidation by KMnO4
Toulene by nitration
Toulene by sulphonation
X is C6H5 - CN ; Y is C6H5 - COOH