The Synthesis Of3,4-dimethylaniline

3,4-dimethylaniline was prepared by selective nitration and catalytic hydrogenation, using o-xylene as staring material.According to the structural features of o-xylene, selected appropriate additives, the regioselectivity of nitration products were investigated by mixed acid as the nitration reagent. The effects of the ratio of mixed acid, nitrifying capacity, reaction temperature and reaction time ect. to conversion rate and regioselectivity of nitration products. The results show that, when the mass fraction of P2O5, nitric acid rate and D.V.S. are respectively controlled at4.5%,1.15and3.16under the temperature of20℃for4hours, nitration of o-xylene shows high regioselectivity. And the ratio of2,3-dimethylntrobenzene to3,4-dimethylntrobenzene is up to0.94in the nitration product,which is much lower than the ratio of1.37when mixed nitric and sulfuric acids are used as nitrating agent.The conversion of o-xylene is97.6%.3,4-dimethylaniline was prepared by catalytic hydrogenation with Raney Nickel Catalyst, using3,4-dimethylntrobenzene as staring material. Effects of hydrogenation have been investigated under the optimized conditions [w(catalyst/substract)=5%in ethanol, initial concentration of the substrate=1.25mol/L,60℃and0.8MPa], both reactant conversion and the purity of3,4-dimethylaniline can be up to100%.