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芳香肼是合成杂环化合物的重要原料,笔者进行了由芳胺合成芳香肼的研究,共合成了7个芳香肼:邻-甲苯肼、对-甲苯肼、对-氯苯肼、邻-甲酸苯肼、间-硝基苯肼盐酸盐、对-硝基苯肼、对-磺酸苯肼,在实验操作中,进行了以下改进:采用SnCl_2作还原剂,使操作简便;制得肼的盐酸盐后,用1∶1盐酸重结晶,防止形成肼后提纯步骤过多,使肼被氧化;萃取前先过滤,提高萃取效率。实验说明,由于重氮化和SnCl_2·2H_2O还原是放热过程,会导致体系温度升高分解重氮盐,反应必须在冰水浴中进行.芳胺是弱碱,要形成铵正离子反应必须在强酸性条件下进行,重氮化反应严重受取代基吸电子效应的影响,氨基甲苯的重氮化很易进行,而硝基苯胺重氮化相当困难。取代基位置也影响重氮化速度,吸电子基团严重防碍邻、对位氨基重氮化.从以下收率数据:邻-甲苯肼61％,邻-甲苯肼盐酸盐55.7％,对-氯苯肼57.1％,对-氯苯肼盐酸盐52.7％,邻-羧酸苯肼65％,对-甲苯肼盐酸盐31.6％,对-磷酸苯肼47.8％,对-硝基苯肼49.2％,间-硝基苯肼盐酸盐50.1％可以看出,收率受重氮化和还原作用双重影响,邻-甲苯肼,对-氯苯肼重氮化很易进行,产率高,间-硝基苯肼、对-硝基苯肼重氮化难进行,但由于形成的重氮盐很稳定易被还原,所以产率比邻-羧酸苯肼、对-磺酸苯肼高,一般芳香肼是?
Aromatic hydrazine is an important raw material for the synthesis of heterocyclic compounds. The author conducted a study on the synthesis of aromatic hydrazines from aromatic amines. Seven aromatic hydrazines were synthesized: o-tolylhydrazine, p-toluhydrazine, p-chlorophenylhydrazine, Phenylhydrazine, m-nitrophenylhydrazine hydrochloride, p-nitrophenylhydrazine, p-sulfonic acid phenylhydrazine, in the experimental operation, the following improvements: The use of SnCl_2 as a reducing agent, so easy to operate; prepared hydrazine Hydrochloric acid, recrystallization with 1: 1 hydrochloric acid to prevent the formation of hydrazine after purification steps too much, the hydrazine is oxidized; extraction before filtration to improve the extraction efficiency. The experimental results show that diazotization and SnCl_2 · 2H_2O reduction are exothermic processes, which leads to the decomposition of diazonium salts by the temperature rise of the system, and the reaction must be carried out in an ice-water bath. The aromatic amine is a weak base, Under the condition of strong acidity, the diazotization reaction is seriously influenced by the electron-attracting effect of the substituent. The diazotization of aminotoluene is very easy, and the diazotization of nitroaniline is quite difficult. The position of the substituent also affects the rate of diazotization, and the electron-withdrawing group severely hampers the diazotization of o- and p-amino acids from the following yield data: 61% ortho-toluhydrazide, 55.7% o- -chlorophenylhydrazine 57.1%, para-chlorophenylhydrazine hydrochloride 52.7%, o-carboxy phenylhydrazine 65%, p-tolylhydrazine hydrochloride 31.6%, p-phenyl phosphate hydrazine 47.8%, p-nitrobenzene Hydrazine 49.2%, m-nitrophenylhydrazine hydrochloride 50.1% can be seen, the yield double effect by the diazotization and reduction, o-toluidine, para-chlorophenyl hydrazine diazotization easily, the yield High, m-nitrophenylhydrazine, p-nitrophenyl hydrazine diazotization difficult, but due to the formation of diazonium salt is very stable and easy to be reduced, so the yield than o-carboxy phenyl phenyl hydrazine, p-sulfonic acid phenyl hydrazine High, the general aromatic hydrazine is?