Experiment 102

Objective

To prepare aniline from nitrobenzene using stannous metal and concentrated hydrochloric acid.

Introduction

In this experiment, nitrobenzene is reduced to aniline. Stannous metal (tin) reacts with concentrated hydrochloric acid, producing hydrogen free radicals. These radicals reduce nitrobenzene, forming aniline through the following reaction:

Reaction:

Sn + 4HCl → SnCl4​ + 4[H]

These free hydrogen radicals then reduce nitrobenzene to aniline.

Materials

Chemicals

·       Stannous metal (tin)

·       Nitrobenzene

·       Hydrochloric acid (HCl)

Apparatus

·       Flask

·       Bunsen burner

·       Stand

·       Water bath

·       Thermometer

·       Collecting glass tube

Reagents

·       10-15 ml of nitrobenzene

·       30-40 ml of concentrated HCl

·       Stannous metal

Procedure

1.    Add hydrochloric acid and stannous metal to the flask.

2.    Place the flask on the stand and immerse it in a water bath.

3.    Heat the mixture at 70°C for 30 minutes.

4.    Using a pipette, add nitrobenzene to the heated mixture.

5.    Aniline will form as aniline hydrochloride salt.

6.    Add NaOH to neutralize HCl, releasing aniline as a brown, oily liquid.

7.    Isolate the aniline in its pure form.

Observation

A brown, oily liquid separates from the solution, which is identified as aniline.

Questions

1.    What is aniline?

2.    How is the hydrogen free radical produced in the reaction between Sn and HCl?

3.    How does the hydrogen free radical reduce nitrobenzene?

4.    Why is tin used for aniline production?