Molecular formula of an aromatic compound is C₈H_10. It is having four isomers A,B,C and D.

Compound (A) on mono nitration gives three nitro substituted compounds and on oxidation with hot alkaline KMnO₄ will give an acid (X) C₇H₆O₂. Compound (B) on mono nitration gives two mono nitro derivatives and on oxidation with hot alkaline KMnO₄ gives an acid (Y) C₈H₆O₄. Y on heating looses water molecule and forms (Z) C₈H₄O₃. Compound (C) on mono nitration gives three mono nitro derivatives .

Compound (D) on mono nitration gives only one nitro derivative. Both compounds (C) and (D) on oxidation 

with hot alkaline KMnO₄ forms compound (P) and (Q) having same molecular formulae C₈H₆O₄ respectively.