Study On The Synthesis Of Red Bases Of Nitroaniline

The derivatives of nitroaniline are important intermediates of organic pigment and color bases of ice dyeing dyestuff. They are also used as intermediates of other organic synthesis after the nitro is reduced to amino.The synthesis of 2-nitro-4-toluidine (red base GL, GL for abbreviation) was studied as emphasis. GL was prepared from p-toluidine via acylation, nitration and hydrolysis. First GL was synthesized with glacial acetic acid as the acylating agent via stepwise synthesis, the molar ratio of p-toluidine and glacial acetic acid was 1∶1.5, the temperature and time of acylation was 240℃, 9h. The total yield was 86.1% and the amino value was 91.22%. Then the process technology was improved. Acetic anhydride was used as the acylating agent instead of glacial acetic acid, fuming nitric acid was used as the nitrating agent and 1,2-dichloroethane was used as the solvent which could be recovered. Three steps of acylation, nitration and hydrolysis were combined in one reactor. The amount of p-toluidine was 0.1mol, the temperature and time of acylation, nitration and alkaline hydrolysis was 80℃, 1h, 45℃, 1h, 97℃, 1.5h, respectively, the excessive acid was removed after nitration. The effect of acetic anhydride, 1,2-dichloroethane, fuming nitric acid and recovery of solvent on yield and purity of GL were researched. The optimum ratio of reactants determined by experiments were as follows: the molar ratio of p-toluidine and acetic anhydride was 1∶1.15, the molar ratio of p-toluidine and fuming nitric acid was 1∶2.6, use amount of 1,2-dichloroethane was 105mL. The yield of GL was 87.9% and the amino value was 97.59%. The yield increased with recovered solvent, could reach 89.3% and the amino value was 98.85%.Additionally, the synthesis of 4-nitro-2-toluidine (red base RL, RL for abbreviation) and 4-nitro-2-methoxylaniline (red base B) was studied. RL was synthesized with acetic anhydride as the acylating agent via stepwise synthesis. The total yield was 56.4% and the amino value was 91.26%. Red base B was synthesized as the similar method and reaction condition of synthesizing GL, the yield was 88.8% and the amino value was 95.77%. The purified yield was 74.2% and the amino value was 98.24%.