Experiment 103

Objective

To prepare aniline yellow (4-amino azobenzene) from benzene diazonium chloride via a coupling reaction.

Introduction

Aniline yellow is synthesized through a coupling reaction between benzene diazonium chloride and aniline in an acidic medium. This reaction yields 4-amino azobenzene, also known as aniline yellow, which appears as a yellow-colored compound.

Materials

Chemicals

·       Benzene diazonium chloride

·       Hydrochloric acid (HCl)

·       Aniline

Apparatus:

·       Test tube

·       Test tube holder

·       Thermometer

·       Dropper

Reagents

·       5–6 ml of aniline and HCl mixture

·       Benzene diazonium chloride, added dropwise

Procedure

1.    Place the aniline and HCl mixture in a test tube.

2.    Add benzene diazonium chloride dropwise to the mixture.

3.    Maintain the temperature below 10°C throughout the reaction (use a thermometer to monitor).

4.    Stop the reaction once the solution turns a uniform yellow color.

Observation

A yellow-colored solution, indicating the formation of aniline yellow, is observed in the test tube.

Questions

1.    What is aniline yellow?

2.    What is diazonium salt?

3.    How is diazonium salt formed?

4.    How is aniline yellow formed?