Experiment 77

Objective

To identify the presence of propanone in a carbonyl compound by detecting iodoform formation.

Introduction

Propanone reacts with iodine in the presence of ammonium hydroxide to form iodoform, which precipitates as a yellow solid. This color change is indicative of the presence of propanone.

Reaction:

CH3​COCH3 ​+ I2 ​+ NH4​OH → CHI3​(yellow ppt) + (CH3​COO)NH4 ​+ H2​O

Materials

Chemicals

●      Propanone

●      Ammonium hydroxide

●      Iodine

Apparatus

●      Test tube

●      Test tube holder

●      Thermometer

●      Dropper

Reagents

●      6–7 ml of propanone

●      6–7 ml of iodine, added dropwise to the propanone solution

Procedure

1.    Place the propanone sample in a test tube and secure it in a test tube holder.

2.    Add 6–7 ml of ammonium hydroxide to the test tube.

3.    Add iodine dropwise to the propanone solution.

4.    Heat the mixture for 10–12 minutes using a Bunsen burner.

5.    Stop heating once a yellow precipitate of iodoform forms.

Observation

A yellow precipitate, identified as iodoform, appears in the solution, confirming the presence of propanone.

Questions

1.    What is iodoform?

2.    How is iodoform formed in this reaction?

3.    How is propanone tested using this method?

4.    What color precipitate forms during the iodoform reaction?