Aniline is an aromatic primary amine compound. Aniline belongs to Nitrogen substituted organic compounds. In this tutorial, you can learn aniline preparing, reactions and characteristics of aniline. Aniline has some different characteristics than other primary amines.
In this tutorial, we study about followings.
Preparation of aniline from benzene is explained below.
There are two steps to prepare aniline from benzene.
Benzene reacts with concentrated sulfuric acid and concentrated nitric acid on heating about 400C and give nitrobenzene. A -NO2 group is substituted to the benzene ring.
Aniline is prepared by the reaction of nitrobenzene and Sn / concentrated HCl / excess NaOH with nitrobenzene. In this reaction, nitrobenzene is reduced to aniline salt by Sn / concentrated HCl. Then aniline is recovered by adding NaOH.
Aniline is an activataor and it is also an ortho para director. We study following aniline reactions. Electrons density of benzene ring in aniline is much higher than benzene.
Secondary amines or tertiary amines or quaternary ammonium salts can be given from reaction of aniline and alkyl halides. The product depends on the amount of aniline and alkyl halide.
Secondary amines are given.
Tertiary amines are given by the reaction of aniline and excess alkyl halide. If there are more alkyl halides, quaternary ammonium salts are given.
Aniline reacts with liquid bromine to give 2-4-6-tribromoaniline.
Aniline reacts with liquid chlorine to give 2-4-6-trichloroaniline.
This reaction is used to prepare phenol or benzene diazonium chloride. Sodium nitrite and dilute hydrochloric acid ( NaNO2 and HCl ) are mixed to prepare nitrous acid (HNO2). According to the temperature, phenol or benzene diazonium chloride is given.
Nitrous acid is prepared by mixing sodium nitrite and dilute hydrochloric acid. ( NaNO2 / HCl ). Aniline reacts with nitrous acid in two ways.
When reaction occurs below 50C, benzene diazonium chloride is given as the product.
In room temperature or above 100C, phenol is given as the product of aniline and nitrous acid reaction.
Aniline has weak basic characteristics. HCl is a strong acid. Aniline reacts with HCl and forms Aniline hydrochloride which has weak acidic characteristics.
Aniline hydrochloride - C6H5NH3+Cl-
Aniline is a primary amine. But some of aniline reactions differ from other primary amine reactions. As an example aniline gives benzene diazonium salt with nitrous acid below 50C. But other primary aliphatic amines give primary alcohols with nitrous acid below 50C.
It takes only two steps. First benzene is converted into nitrobenzene. Then nitrobenzene is converted to aniline.
We know, aniline is basic and phenol is acidic. So aniline can react with acids and phenol reacts with bases.
Electrons density of benzene ring in aniline is higher than benzene. Therefore electrophilic substitution reactions are occurred easily than benzene.
Example: Aniline reacts with bromine liquid to give 2,3,4-dibromoaniine. But benzene does not give products with Br2(l). Benzene requires a lewis acid catalyst to give products with Br2(l)
Aniline is a weak base. It reacts with HCl and forms a weak acid (phenylammonium chloride).