Experiment 86

Objective

To prepare chloroform (CHCl₃) in the laboratory from propanone (acetone) using bleaching powder and water.

Introduction

Chloroform is synthesized by reacting propanone with bleaching powder and water in a three-step process:

1.    Formation of Chlorine

o   Bleaching powder reacts with water to produce chlorine and calcium hydroxide:

Ca(OCl)Cl + H2O → Ca(OH)2 + Cl2

2.    Reaction of Chlorine with Propanone

o   Chlorine then reacts with propanone to form 1,1,1-trichloropropanone and hydrochloric acid:

CH3 ​-CO-CH3​ + Cl2​ → CCl3​-CO CH3 + HCl

3.    Formation of Chloroform

o   1,1,1-Trichloropropanone reacts with calcium hydroxide, producing chloroform and calcium acetate:

CCl3-CO-CH3 ​+ Ca(OH)2 ​ → CHCl3  ​+ (CH3​COO)2Ca

 Materials

Chemicals

●      Propanone (CH₃COCH₃)

●      Bleaching powder (Ca(OCl)Cl)

●      Distilled water

Apparatus

●      Flask

●      Bunsen burner

●      Stand and sand bath

●      Beaker for chloroform collection

●      Thermometer

Reagents

●      Mix 3.625 g of bleaching powder with twice its weight in water, and 10 mL of 100% pure propanone.

Procedure

1.    Preparation of Bleaching Powder Solution

●      Combine bleaching powder with twice its weight of water in a flask.

2.    Addition of Propanone

●      Add propanone to the flask and mix well.

3.    Setup for Collection

●      Attach a thermometer and a glass tube for chloroform collection at the mouth of the flask. Connect the tube to a beaker for collecting chloroform.

4.    Heating the Mixture

●      Place the flask in a sand bath and heat gently with a Bunsen burner.

5.    Collection of Chloroform

●      The produced chloroform is condensed and collected in the beaker through the connecting tube.

6.    Purification

●      To obtain 100% pure chloroform, add NaOH, followed by CaCl₂, and distill the mixture.

Observation

The chloroform collects in the beaker and displays characteristic properties.

Questions

1.    What happens when a mixture of propanone, bleaching powder, and water is heated?

2.    What is chloroform?

3.    What occurs when chloroform reacts with water?