Experiment 100

Objective

To prepare alkyl cyanide (methyl cyanide) by reacting an alkyl halide with an inorganic cyanide salt.

Introduction

Alkyl halides react with potassium cyanide (KCN) or sodium cyanide (NaCN) to form alkyl cyanides. In this experiment, methyl iodide is reacted with alcoholic potassium cyanide under heat, resulting in the formation of methyl cyanide (acetonitrile) and potassium iodide.

Reaction:

CH3​I + KCN → CH3​CN + KI

Materials

Chemicals

●      Methyl iodide (CH₃I)

●      Potassium cyanide (KCN)

Apparatus

●      Two test tubes

●      Two test tube holders

●      Bunsen burner

Reagents

●      3.659 g of KCN

●      Equivalent amount of methyl iodide

Procedure

1.    Place the KCN and methyl iodide in a test tube.

2.    Secure the test tube in a holder.

3.    Heat the mixture for 1–2 minutes using a Bunsen burner.

4.    Stop heating once a colorless liquid, methyl cyanide, is produced.

Observation

A clear liquid, methyl cyanide, is produced in the test tube. Caution: Methyl cyanide is hazardous.

Questions

1.    What is methyl cyanide?

2.    How is methyl cyanide formed?

3.    What reagents are used to form methyl cyanide?