What is the preparation of p nitroaniline? Learn more

What is the preparation of p nitroaniline? P nitroaniline is a chemical compound used in the synthesis of other chemicals. P nitroaniline is an aniline that has been acetylated with nitrous acid and acetic anhydride. It reacts with chlorine, hydrogen chloride, and metal halides to give a variety of substituted aromatic compounds called chloroanilines. It also reacts with ammonia to produce the monochloramine (NHCl), dichloramine (NHCl), hypochlorite ion (HOCl), and nitrogen dioxide (NO₂).

Preparation of p nitroaniline

Below are some of the methods described for the preparation of p nitroaniline:

1. Preparation from nitro-nitrosamines

The synthesis of p nitroaniline from substituted anilines is a common method used. It is easier to prepare from substituted anilines such as 2-nitrodiphenylamine. In this method, diphenylamine (diphenylamine), together with acetic anhydride, is reacted with hydrogen chloride in the presence of a catalyst such as zinc chloride in a concentrated sulfuric acid solution. The reaction is completed by evaporation and subsequent distillation of the reaction mixture. The yield is only about 0.2%.

This method involves the debenzylation of substituted anilines with sodium in the presence of a catalyst such as boron trichloride and dimethyl sulfate. The reaction is completed by evaporation and subsequent distillation of the reaction mixture. The yield is only 5% - 7%.

This method is effective for the preparation of substituted anilines such as 2-nitrodiphenylamine. It involves reacting diphenylamine with sodium in concentrated sulfuric acid solution, which are boiled together with concentrated hydrochloric acid. The reaction is completed by evaporation and subsequent distillation of the reaction mixture. The yield is about 60%.

2. Preparation from nitroamines

This method involves the rearrangement of nitro compounds through acid catalyzed reactions. In this method, one nitro compound is attacked by an aqueous solution of alkali metal hydroxide such as sodium hydroxide in the presence of acid catalysts such as aqueous hydrogen chloride solution or anhydrous magnesium sulfate. The reaction is completed by evaporation and subsequent distillation of the reaction mixture. The yield is about 95%.

3. Preparation from substituted anilines

In this method, one substituted aniline is reacted with hydrogen chloride in concentrated sulfuric acid solution to obtain p nitroaniline directly without any intermediate compound. The reaction is complete when the mixture is boiled with concentrated hydrochloric acid.

4. Preparation from nitroaniline

In this method, nitroaniline is transformed into p nitroaniline through the acid-catalyzed rearrangement of the nitro group. In this method, an aqueous solution of alkali metal hydroxide such as sodium hydroxide in the presence of an acid catalyst such as hydrogen chloride is reacted with nitroaniline. The reaction is complete when the mixture is boiled with concentrated hydrochloric acid.

5. Preparation from chloroanilines

This method involves the conversion of chloroanilines into p nitroaniline and then back to chloroanilines. Nitroaniline is reacted with hydrogen chloride in concentrated sulfuric acid solution in the presence of acid catalysts such as aqueous sodium hydroxide or anhydrous magnesium sulfate to obtain p nitroaniline by the dehydration of nitroaniline. This method is preferred than other methods since the yield is high and the reaction is quick. The yields are 100% - 98% depending on the reaction conditions.

6. Preparation from hydrogen chloride

The reaction of chloroanilines with hydrogen chloride leads to p nitroaniline. However, this method is disadvantageous because the yield of p nitroaniline is low and the reaction may be slow. The reaction of chlorine with aniline or substituted anilines reacts in a two step process. First they react by alkylation or reductive amination and then they add Cl to their "parent" structure.

7. Preparation of p nitroaniline from substituted amines

This method involves the preparation of p nitroaniline from substituted amines and is usually performed in four steps. First, anilines are prepared by treating the corresponding benzyl halides with an alkaline solution of hydrazine hydrate in ethanol. The reaction is complete when the mixture is concentrated and allowed to cool. The yields are about 75%.

Next, 1-chloroaniline is prepared by reacting p nitroanilin with N-chlorosuccinimide. The reaction is complete when the mixture is left to stand overnight at room temperature and then distilled off the water and other volatile materials. The reaction with chlorine gas yields 1-chloroaniline directly.

Conclusion

The production of p nitroaniline is an essential part of the preparation of chloroanilines. Chloroanilines are used in the manufacturing process of herbicides, fungicides, dyes, rubber accelerators, and photographic chemicals. This chemical is also used in gas masks, protecting the respiratory tract from the harmful effects of toxic gases such as chlorine. P nitroaniline is not only safe to use and stable under most conditions but also easy to handle with a low toxicity level.