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Haloalkanes And Haloarenes

Question
CBSEENCH12007976

How is pure chloroform prepared? How is it oxidised in air or sunlight?

Solution

In industry, chloroform is produced by heating a mixture of chlorine or methane. At 400–500 °C, a free radical halogenation occurs, converting these precursors to progressively more chlorinated compounds:

CH4 + Cl2 → CH3Cl + HCl

CH3Cl + Cl2 → CH2Cl2 + HCl

CH2Cl2 + Cl2 → CHCl3 + HCl
Chloroform is slowly oxidised by air in the presence of light to an extremely poisonous gas, carbonyl chloride known as phosgene.
2 CHCl subscript 3 space plus space straight O subscript 2 space rightwards arrow with space space space light space space space space space on top 2 COCl subscript 2 space left parenthesis phosgene right parenthesis plus 2 HCl