C2h2--c6h6--(ch3cl,alcl3)--X1--(kmn04)X2
3HC≡CH = C6H6 C6H6+CH3Cl = C6H5CH3+HCl 5C6H5CH3+6KMnO4+9H2SO4 = 5C6H5COOH+3K2SO4+6MnSO4+14H2O