Solution

Etard reaction: toluene is oxidised by chromyl chloride in $CS_2$ to form a chromium complex, which on hydrolysis gives benzaldehyde. $C_6H_5CH_3 + CrO_2Cl_2 \xrightarrow{CS_2} C_6H_5CH(OCrOHCl_2)_2 \xrightarrow{H_3O^+} C_6H_5CHO$ So X is $C_6H_5CH(OCrOHCl_2)_2$.

Concept intermediate in the Etard reaction

Aldehydes, Ketones and Carboxylic Acids in past papers

91 questions from this chapter have appeared across 27 exam years.