Preparation of Aniline Yellow

Introduction

Aniline Yellow is a derivative product of Azobenzene It. has appearance of orange colour in powder form. It was first prepared by C. Mene in 1861. In the year of 1864 it was commercialized as first Azo dye. It is slightly soluble in water and soluble in Ethanol, Benzene, and oil. It is a weak base and forms a salt with Mineral acids.

What is Aniline Yellow?

Aniline Yellow is called Aamino Azobenzene obtained by an easiest coupling reaction.of azo dye. This dye has no industrial significance due to acid sensitive nature.

Figure1 − Chemical Formula of Aniline

In order to obtain pure dye, recrystallization of crude sample is carried out by dissolving it in Carbon Tetrachloridesolvent. Using simple litmus paper test, Aniline Yellow can be identified. As Aniline” is basic in nature so it turns red litmus into blue.

Uses of Aniline Yellow

The uses of Aniline Yellow are discussed below −

• It is used in rubber accelerators.

• Used as dyes and intermediates

• In herbicides and pesticides.

• In petroleum refining and explosives

• In pharmaceuticals and in making explosions

Properties of Aniline

Figure 2 − Molecular structure of Aniline Yellow

It is a yellow, oily liquid, and it gets dark on exposure to air or light. It also has Amine odor and burning taste. It shows weak basic nature and forms salt in presence of mineral acid. ThepH value of Aniline Yellow is 8.8. It is a polar molecule acts as a Hydrogen bond donor. Its toxic naturecan damage haemoglobin and fail to carry oxygen.

Aim of the study

The aim is to prepare Aniline Yellow from Bbenzene Diazonium Chloride and Aniline.

Theory of production of Aniline Yellow

The present study has mentioned about few effective theories on production of effectively. The first stage of preparation of Aniline Yellow starts with the formation of Benzene

Diazonium Chloride from Aniline. For this purpose, Aniline is treated with Sodium Nitrite in presence of acid. It produces Benzene Diazonium Chloride salt. The salt is then coupled with phenylamine to yield yellow precipitate of Para Amino Azobenzene, also known as Aniline Yellow. It is volatile in nature and used as an intermediary in the production of other colors.

Chemical Reaction of the preparation process

The chemical reactions involved in the preparation of Aniline Yellow are discussed below.

Step 1:

$$\mathrm{Ar\:-\:NH_{2}\:+\:NaNO_{2}\:+\:HCl\:\rightarrow\:Ar\:-\:N_{2}^{+}\:.\:Cl^{-}}$$

Step 2:

$$\mathrm{Ar\:-\:N_{2}^{+}.Cl\:+\:Ar\:-\:NH_{2}\:\rightarrow\:Ar\:-\:N\:=\:N\:-\:NH\:-\:Ar}$$

Step 3:

$$\mathrm{Ar\:-\:N\:=\:N\:-\:NH\:-\:Ar\:\rightarrow\:Ar\:-\:N\:=\:N\:-\:Ar\:-\:NH_{2}}$$

In the initial stage, Aniline” acts as a nucleophile thus, reacts with Benzene Diazonium Chloride $\mathrm{C_{6}H_{5}N_{2}^{-}Cl^{-}}$ to form a C-N bond. In the next step, it loses its H+ ion and results in Aazo dye.

Materials required

The required materials for the preparation of Aniline Yellow are discussed below −

• Aniline

• HCl(Hydrochloric acid)

• Sodium Nitrite

• Glacial Acetic acid

• Bunsen Burner

• Distilled water

• Round bottom flask

• Beaker

• Stirrer

• Funnel

• Water bath

• Conical flask

Procedure

The procedures to prepare aniline y Yellow are discussed below −

• 10 mL Hydrochloric acid is taken with 20 mL of water and 4ml of Aniline is added in the mixture.

• Dissolve the mixture completely

• The solution is to be cooled down in the ice bath at approx. 5°C.

• 4g of Sodium Nitrite is added to water and stir it until dissolve completely

• This solution is mixed with the solution of Aniline to prepare Benzene Diazonium Chloride solution

• Add 4mL of Hydrochloric acid and prepare 4ml of Aniline to the Benzene Diazonium Chloride solution. This coupling results in formation of Aniline Yellow

• To obtain the pure dye, recrystallization of crude sample is carried out by dissolving it in Carbon Tetrachloride solvent.

• A pure yellow precipitate is formed known as Aniline Yellow and this Yellow precipitate is filtered through a Buchner funnel and kept for dried down.

Precautions

Precautions for this preparation process are mentioned below −

• Do not touch the dye as it is sticky.

• The temperature of the experiment should be maintained between 40° to 50°

• The pH value of the experiment must be in between 4 to 5.

• The crude sample must be washed repeatedly with water

• While performing this experiment some protections are required such as, lab coats, gloves, and goggles. The reduction of Nitrobenzene is done through Iron borings in aqueous acid.

Conclusion

The temperature of the experiment should not exceed 50℃ to avoid explosion. However, it does not have industrial significance due to its sensitive nature towards acid. Aniline Yellow is produced with the coupling of Benzene Diazonium Chloride with Aniline in acidic medium. Synthesis of Benzene Diazonium Chloride from Aniline is the first step of Aniline Yellow formation. Later on,Azo dye is produced by coupling ofBenzene Diazonium Chloride and Phenylamine.

FAQs

1. Distinguish between Phenol and Aniline chemically?

By a simple litmus paper test it can be identified. As Aniline is basic in nature so it turns red litmus into blue and Phenol is mildly acidic so it turns blue litmus into red.

2. Is Aniline a weaker base than Ammonia?

Aniline is a weaker base than Ammonia in solution because of resonance effect of Benzene ring in Aniline makes less available of lone pir on Nitrogen atom.

3. What is the meaning of Diazotization?

It is a reaction process between Nitrous acid and mineral acid to form Diazonium salt as a product

4. Is Aniline Yellow a dye?

It is a yellow azo dye and an aromatic amine and it also appears as an orange powder.