Study On Synthesis And N-alkylation Of Aromatic Diamines

N-Alkylated aromatic diamines as important intermediates play a key role in organic chemical field. These compounds have well served as antioxidants, dyes, developing agents and other additives. Moreover, N-alkylated aromatic diamines are also utilized in the synthesis of many pharmaceuticals. In this paper, aromatic diamines were effectively synthesized in a total yield of more than 68% with aniline as starting material through acetylation, nitration, hydrolysis and reduction processes. Then, the N-alkylated aromatic diamines were formed by the reaction of aromatic diamines with haloalkanes in the presence of catalysts.Acetanilide was prepared by acetylation of aniline. In the nitration of acetanilide, nitrating systems were discussed. The para nitro-compound was achieved in nitric-sulfuric acids solution with a high yield and selectivity (ortho/para= 12/88). However, acetanilide nitration in nitric-acetic systems resulted in more ortho nitro-compound(ortho/para 66/34). The para nitro-compound was hydrolyzed to form nitroaniline in an acidic condition, which was further reduced to produce aromatic diamine by the use of metal reducing agent.N,N'-Di-sec-butyl-p-phenylenediamine is a widely used antioxidant, which can be prepared by N-alkylation of p-phenylenediamine and 2-bromobutane. In this reaction, various technological parameters such as solvent, catalyst, co-catalyst and feed ratio were discussed. Aprotic solvent was favorable for N-alkylation. Addition of potassium iodide accelerated the reaction. The catalyst KF/Al2O3 offered a highly conversion rate and selectivity (96:4). Zeolite gave a poor conversion rate because of weakly basicity.In this process N-alkylation was further carried out in details. The structures of aromatic amines and haloalkanes, leaving groups, catalysts were discussed. Treatment of p-phenlenediamine and primary haloalkane under basic conditions gave more overalkylation derivatives. As compared, o-phenlenediamine gave poor overalkylation derivatives because of steric effect. The reactivity of chloroalkane was weaker than bromoalkane, but selectivity was still poor. In the N-alkylation of p-oluidine or o-toluidine with 1-borombutane, NaX type zeolite offered a high selectivity (98:2) in favor of monoalkylation derivatives. However, the overalkylation product increased with aromatic diamine as substrate.