Physical and chemical property of Chloroform.

Physical property.

Some of the physical property are as follows.

1. It is colourless and sweet smelling liquid.
2. Freezing point and a boiling point of chloroform are -63⁰C and 61⁰C.
3. It is non-flammable liquid. However, vapour chloroform burned with the green flame.
4. It is insoluble in water and soluble in organic solvent.
5. Although chloroform is non-poisonous, if forms a poisonous compound (phosgene) in air.

Chemical property.

Some of the chemical property are as follows.

1. Oxidation reaction.

Chloroform is oxidised in the air in presence of sunlight to form a poisonous compound called phosgene.

$$2CHCl_3+O_2(air)\xrightarrow{Sunlight}2COCl_2+2HCl$$

Chloroform is stored in a dark brown bottle with a tight lid so as to prevent the formation of poisonous phosgene.

Chloroform containing bottle is often supplied with a small amount of ethanol since it converts phosgene into diethyl carbonate which is non-poisonous.

2. Reduction.

Chloroform is reduced to dichloro methane in acidic and neutral medium respectively.

$$CHCl_3+2[H]\xrightarrow{Zn\,/HCl}CH_2Cl_2+HCl$$

$$CHCl_3+6[H]\xrightarrow{Zn\,/H_2O}CH_4+3HCl$$

3.Hydrolysis.

Chloroform on boiling with aqueous KOH hydrolyzed to form potassium formate.

$$CHCl_3+4KOH \xrightarrow{Heat}HCOOK+3KCl+2H_2O$$

4. Chlorination.

Chloroform on further chlorination gives carbon tetrachloride.

$$CHCl_3+Cl_2 \xrightarrow{hv}CCl_4+HCl$$

5. Action with nitric acid.

Chloroform on heating with concentrated nitric acid forms chloropicrin which is used as an insecticide and war gas.

$$CHCl_3+HNO_3\xrightarrow{Heat}CCl_3NO_2+H_2O$$

6. Action with silver powder.

2CHCl_3+6Ag\xrightarrow{Heat}HC≡CH+6AgCl$$

7. Reaction with Phenol. (Reimer -Tiemann reaction).

When phenol is heated with chloroform and aqueous alkaline at temperature 60-70⁰C, O-hydroxy benzaldehyde (Salicylaldehyde) is formed as the chief organic product. This reaction is termed as Riemer-Tiemann reaction.

8. Reaction with the primary amine.

(Carbylamine reaction)

Chloroform produces an offensive smelling carbylamines or isocyanide when warmed with the Primary amine (R-NH2-aliphatic or aromatic) in presence of an alkali. This reaction is known as carbylamines reaction.

Example.

A haloalkane P reacts with aq. KOH to give Q. The compound Q on oxidation with K₂Cr₂O/H⁺ give R and R undergo Clemmensen reduction to produce S. The compound P reacts with sodium in presence of dry ether to form 2,3 dimethylbutane, Write chemical reactions involved and identify P,Q,R and S.

Answer.

Let identify P at first reacts with sodium metal in the presence of dry ether to give 2,3 dimethylbutane so P should be 2- Haloproparopane.

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.