Experiment 85

Objective

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

Introduction

Chloroform can be synthesized by reacting ethanol with bleaching powder and water in a four-step process:

1.    Formation of Chlorine

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

Ca(OCl)Cl + H2O → Cl2 + Ca(OH)2

2.    Reduction of Ethanol

·       Chlorine then reacts with ethanol to form acetaldehyde (ethanal) and hydrochloric acid:

CH3 ​– CH2 ​– OH + Cl2 ​→ CH3 ​– CHO + 2HCl

3.    Formation of Chloral

·       Acetaldehyde reacts with additional chlorine to produce chloral (CCl₃-CHO) and hydrochloric acid:

CH3 ​– CHO + 3Cl2 ​→ CCl3 – CHO + 3HCl

4.    Formation of Chloroform

·       Chloral reacts with calcium hydroxide, yielding chloroform and calcium formate:

2CCl3 ​– CHO + Ca(OH)2 ​→ 2CHCl3 ​+ Ca(COOH)2

Materials

Chemicals

·       Bleaching powder (Ca(OCl)Cl)

·       Ethanol (CH₃CH₂OH)

·       Distilled water

Apparatus

·       Flask

·       Bunsen burner

·       Stand and sand bath

·       Beaker for chloroform collection

·       Thermometer

Reagents

·       Prepare a solution of 3.625 g of bleaching powder mixed with twice its weight in water and 10 mL of 100% pure ethanol.

Procedure

1.    Preparation of Bleaching Powder Mixture

o   Mix bleaching powder with twice its weight of water in a flask.

2.    Addition of Ethanol

o   Add ethanol to the mixture in the flask and shake well.

3.    Setup for Collection

o   Insert a thermometer and a collecting glass tube in the flask. Connect the tube to a beaker designated for chloroform collection.

4.    Heating the Mixture

o   Place the flask in a sand bath and heat it gently using a Bunsen burner.

5.    Collection of Chloroform

o   Chloroform produced in the reaction condenses and is collected in the beaker through the collecting tube.

6.    Purification

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

Observation

Chloroform, with its characteristic properties, collects in the beaker.

Questions

1.    What is chloroform?

2.    What is ethyl (ethanal)?

3.    What happens when bleaching powder and water are combined?

4.    How is chloroform produced?