P on treatment with Br 2 / FeBr 3 in CCl 4 produced a single isomer C 8 H 7 O 2 Br wile heating P with sodalime gives toluene. The compound P is:

Step-by-step solution

Isomer C 8 H 7 O 2 Br on heating with sodalime gives toluene,hence it is an acid.Moreover since it has Degree of unsaturation 5 therefore it is an aromatic carboxylic acid.Since Carboxylic acid on heating gives toluene ,therefore it is having - CH 3 group attached to the benzene ring. Now it forms single isomer on halogenation, therefore - CH 3 group must be attached at para position with respect to - COOH group. Hence correct option is 1.