Experiment 94

Objective

To prepare toluene (methylbenzene) in the laboratory using the Wurtz-Fittig reaction.

Introduction

The Wurtz-Fittig reaction involves reacting an alkyl halide (e.g., methyl iodide) with an aryl halide (e.g., bromobenzene) in dry ether with sodium metal, producing toluene. This reaction occurs as sodium induces the coupling of the halides in a non-aqueous environment.

Materials

Chemicals

·       Bromobenzene

·       Dry ether

·       Sodium metal

·       Methyl iodide

Apparatus

·       Flask

·       Bunsen burner

·       Stand

·       Thermometer

·       Beaker (for toluene collection)

·       Ice pieces

Reagents

·       Combine bromobenzene and methyl iodide in dry ether with sodium metal.

Procedure

1.    Preparation of Reaction Flask

o   Place the reaction flask in an ice bath.

2.    Addition of Reactants

o   Add dry ether to the flask, followed by a piece of sodium metal.

3.    Addition of Alkyl and Aryl Halides

o   Gradually add methyl iodide and bromobenzene to the flask.

4.    Reflux Reaction Mixture

o   Reflux the mixture and wait for the reaction to produce toluene.

5.    Collection of Toluene

o   Attach a tube from the flask to a beaker for collecting toluene.

o   Heat the reaction mixture to approximately 110°C, allowing pure toluene to distill into the beaker.

Observation

Toluene condenses in the beaker, appearing as an oily liquid with characteristic physical properties.

Questions

1.    What is toluene, and what is its general formula?

2.    What is the Wurtz-Fittig reaction?

3.    Why is sodium used in the Wurtz-Fittig reaction?

4.    Why is dry ether used in the Wurtz-Fittig reaction?