(1)Benzene + CH3-Cl in presence of AlCl3(Cat.)ie F.C. alkylation =>toulene
(2)Toulene + H2SO4/HNO3(nitration) =>p-nitro Toulene .
(nitro is at para positionbecause CH3 is activating group directs the reaction to the ortho or para postion,which means the E+ ie NO2 substitute on para position.why toulene is not treated with KMnO4 in 2nd step ?because If toulenle treated with KMnO4 in 2nd step it will produce benzoic acid which will be deactivating group,which means E+ ie NO2 will cm at meta postion)
(3)p-nitro toulene +KMnO4(O) =>p- nirto Benzoic acid
(4)p-nitro benzoic acid +LiAlH4/ether or B2H6 => p-nitrobenzyl alcohol
(5)p-nitrobenzylalcohol =K2Cr2O7/H2SO4(jones reagent) with PCC => p-nitro Benzaldehyde