The Study Of The Synthesis Process Of P-nitrobenzaldehyde

4-Nitrobenzaldehyde is an important intermediate in the synthesis of pharmaceutical, dyestuffs and other fine chemicals.In this dissertation,the preparation of 4-nitrobenzaldehyde was studied.Reaction of benzyl alcohol with acetic anhydride gave benzyl acetate.Nitration of benzyl acetate with HNO₃ in the presence of Nb₂O₅(3%weight percent)at 0～10℃for 0.5 hours gave mononitro products in 93%yield with 83～88%para selectivty.Nb₂O₅ was recovered by filtration and reused in the nitration for 5 times without significant loss of the yield ofmononitro products and para selectivty.To avoid benzyl ether formation,acid hydrolysis of nitrobenzyl acetate,Magnesium catalyzed hydrolysis of nitrobenzyl acetate in methanol and Alkaline hydrolysis of nitrobenzyl acetate in the organic solvent were studied.Acid hydrolysis of nitrobenzyl acetate at 95℃for 6 hours in aqueous sulfuric acid gave nitrobenzyl alcohol in 76%yield.Magnesium catalyzed hydrolysis of nitrobenzyl acetate at room temperature for 0.5 hours in methanol gave nitrobenzyl alcohol in 82%yield.Alkaline hydrolysis of nitrobenzyl acetate at room temperature for 0.5 hours in mixed solvent of CH₂Cl₂ and CH₃OH gave nitrobenzyl alcohol in 87%yield.Recrystallization of the crude product from toluene gave 4-nitrobenzyl alcohol in 62%yield with 99%purity.4-Nitrobenzaldehyde was obtained in 84%yield with 99%purity via ionic liquid immobilized TEMPL/CuCl/3AMS catalyzed oxidation of 4-nitrobenzyl alcohol with molecular oxygen in ionic liquid[bmim]PF₆.The oxidation condition is mild,the selectivity is high,and no 4-nitrobenzoic acid is detected in any case.The catalytic system was recovered and reused for 3 times without significant loss of catalytic activity.