Laboratory preparation of Chloroform.

Chloroform. (CHCl)₃.

Chloroform is a sweet smelling liquid having freezing point -63⁰C. and has boiling point 61⁰C. it is the colourless non-flammable liquid that is insoluble in water.

Preparation ofChloroform

It is prepared by following methods.

1. From methane.

On an industrial sacle,chloroform is prepared by chlorination of methane.

$$CH_4\xrightarrow{hv/Cl_2\,-HCl}CH_3Cl\xrightarrow{Cl_2\,/-HCl}CH_2Cl_2\xrightarrow{Cl_2\,/-HCl}CHCl_3=(Chloroform)$$

2. From carbon tetrachloride.

Chloroform can also be prepared on the industrial scale by partial reduction of carbon tetrachloride with iron filings and stream.

$$CCl_4+2[H]\xrightarrow{Fe/H_20/Heat}CHCl_3+HCl$$

$$CHCl_3=(Chloroform)$$

3. From choral hydrate.

Pure chloroform is prepared by heating choral hydrate with a strong solution of caustic soda.

$$CCl_3CH(OH)_2+NaOH\xrightarrow{heat}CHCl_3+HCOONa+H_20$$

$$CCl_3CH(OH)_2=Choral\,hydrate$$

$$CHCl_3=(Chloroform)$$

Laboratory preperation of Chloroform.

Principle

Chloroform. is prepared in the laboratory by heating a mixture of Bleaching powder with ethanol or acetone. In this reaction, bleaching powder acts as oxidising chlorinating and hydrolyzing agent.

$$CaOCl_2+H_20→Ca(OH)_2+Cl_2$$

$$CaOCl_2$$

Chlorine gas evolved from bleaching powder paste oxides and chlorinates ethanol. Moreover, it chlorinates acetone as well.

The various reaction involves are as follows.

[I] In a case of ethanol.

[II] In a case of acetone.

Procedure.

In round bottom flask, bleaching powder paste is prepared by adding 100g of bleaching powder to 200 ml of water and crushing the residue of bleaching powder in a mortar with the help of a pestle. the solution is then filtered into 1 1000ml of the round-bottomed flask. After that 25 ml of ethanol or acetone is added to it. The flask is then fitted with a water condenser at the other end of which a receiver is joined. The flask is then placed over sand bath and heated till a mixture of chloroform and water distills over. The mixture from the receiver is transferred to a separating funnel and the lower layer of chloroform is separated.

Purification.

Chloroform obtained by heating bleaching powder paste with acetone or ethanol is not in pure form. To remove impurities, it is passed through dilute caustic soda solution and washed with water in a separating funnel. The chloroform is then dried over anhydrous CaCl₂ and redistilled between the temperature 60⁰C-65⁰C.

Uses of Chloroform.

Chloroform is a sweet smelling liquid which is used for the following a purpose.

1. It is used as the solvent for the production of dyes and pesticides.
2. Chloroform is mostly used tools in kidnapping especially in books and movies.
3. Chloroform usually contain heavy metal like deuterium which is used for solvent as Nuclear Magnetic Resonance (NMR) Spectroscopy.

Reference.

Bahl, B S, Bahl, and Arun. Advanced Organic chemistry. S. Chand and company Ltd., n.d.

Sthapit, M K, R R Pradhananga, and K B Bajracharya. Foundations of chemistry. Taleju Prakashan, n.d.

Tewari, K S, S N Mehrotra, and N K Vishnoi. A textbook of organic chemistry. Vikash publishing House Pvt. ltd., n.d.

Verma, N K and S K Khanna. Compressive chemistry. 8th edition. Laxmi publications P. Ltd., 1999.