Experiment 106

Objective

To prepare butter yellow (4-(N,N-Dimethylamino) azobenzene) from benzene diazonium chloride.

Introduction

Butter yellow, or 4-(N,N-Dimethylamino) azobenzene, is synthesized through a coupling reaction between benzene diazonium chloride and N,N-dimethyl aniline in an acidic medium. This reaction produces a distinct yellow compound known as butter yellow.

Materials

Chemicals

·       Benzene diazonium chloride

·       Hydrochloric acid (HCl)

·       N,N-Dimethyl aniline

Apparatus

·       Test tube

·       Test tube holder

·       Thermometer

·       Dropper

Reagents

·       5–6 ml of N,N-dimethyl aniline and HCl mixture

·       Benzene diazonium chloride, added dropwise

Procedure

1.    Place the N,N-dimethyl aniline and HCl mixture in a test tube.

2.    Add benzene diazonium chloride dropwise to the test tube.

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

4.    Stop the reaction once the solution turns a consistent butter-yellow color.

Observation

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

Questions

1.    What is butter yellow?

2.    What is diazonium salt?

3.    How is diazonium salt formed?

4.    How is butter yellow formed?