A brown chromium complex is formed as an intermediate when a hydrocarbon 'X' is treated with a reagent 'Y'. The hydrolysis of this complex yields an aldehyde 'Z' which reduces Tollens' reagent but does not reduce Fehling's solution. Identify 'X' and 'Y'.

Step-by-step solution

Aldehyde 'Z' reduces Tollens' reagent but not Fehling's solution, which is a characteristic property of aromatic aldehydes such as benzaldehyde. The formation of a brown chromium complex intermediate during the oxidation of a hydrocarbon to benzaldehyde is the hallmark of the Etard reaction. In the Etard reaction, toluene (hydrocarbon 'X') is treated with chromyl chloride ( CrO ₂ Cl ₂ ) in a non-polar solvent like CS ₂ (reagent 'Y') to form the brown chromium complex, which on subsequent acid hydrolysis gives benza