Polyhalogen Derivatives - Carbon tetrachloride

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Many polyhalogenated hydrocarbons find important use as industrial solvents, pesticides, refrigerants, medicines, inert lining of cooking utensils, etc. Some useful chloro compounds are:

Carbon tetrachloride (CCl₄)

It is prepared industrially by the following methods:

From methane

Carbon tetrachloride can be prepared by the chlorination of methane in the presence of sunlight.

From carbon disulphide

Carbon tetrachloride is prepared by the action of chlorine on carbon disulphide in the presence of AlCl₃ (catalyst).

Carbon tetrachloride is separated from S₂Cl₂, by fractional distillation.

Physical Properties of Carbon Tetrachloride

• Carbon tetrachloride is a colorless oily liquid with sickly smell.

• It is insoluble in water but is soluble in organic solvents such as ether, alcohol.

• Its boiling point is 350 K.

• The vapours of carbon tetrachloride are inflammable.

Chemical Properties

Reduction

On reduction with moist iron filings, CCl₄ gives chloroform.

Hydrolysis

On passing steam, the vapors of CCl₄ decompose to give phosgene (poisonous gas).

Action with KOH

On heating with alcoholic KOH, it decomposes to give CO₂. The CO₂ dissolves in KOH to give potassium carbonate.

Action with antimony trifluoride

Carbon tetrachloride reacts with SbF₃ in the presence of antimony pentachloride as catalyst to give dichlorodifluoromethane (freon).

Freon is easily liquefied and is used as refrigerant and propellant in aerosols.

Uses

• As a solvent for oils, fats, waxes, etc.

• As a fire extinguisher under the name pyrene.

• In dry cleaning.

• In the manufacture of freon.