C->CaC2->C2H2->C6H6->C6H5->CH3->C6H5COOH
3C+caO =CaC2 + CO
CaC2+H2O = Ca(OH)2 + C2H2
3C2H2 = C6H6
C6H6 + CH3Cl = C6H5CH3 + HCl
C6H5CH3 + 3O = C6H5COOH + H2O