Question

Explain the preparation of the following compound.

Chloroform

Answer 1

Chloroform is prepared in the laboratory by the reaction between ethyl alcohol with bleaching powder followed by the distillation of the product chloroform. Bleaching powder act as a source of chlorine and calcium hydroxide. This reaction is called the haloform reaction. The reaction proceeds in three steps as shown below.

Step – 1: Oxidation

\[\ce{\underset{\text{Ethyl alcohol}}{CH3CH2OH} + Cl2 -> \underset{\text{Acetaldehyde}}{CH3 CHO +}2HCl}\]

Step – 2: Chlorination

\[\ce{\underset{\text{Acetaldehyde}}{CH3 CHO +} 3Cl2 -> \underset{\text{Trichloro acetaldehyde}}{CCl3 CHO +} 3HCl}\]

Step – 3: Hydrolysis

\[\ce{\underset{\text{Chloral}}{2CCl3CHO} + Ca(OH)2 ->\underset{\text{chloroform}}{2CHCl3} + (HCOO)2Ca}\]