Briefly explain Photohalogenation of Alkanes:

Briefly explain Photohalogenation of Alkanes:


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askIITIians Expert
21 Points
14 years ago


Photohalogenation of Alkanes:

By direct halogination of paraffins in the presence of light or catalyst. The order of ease of substitution is tertiary hydrogen atom > secondary hydrogen atom > primary hydrogen atom. During chlorination every possible monochloride is obtained and chlorination beyond mono substitution may be supressed by controlling the ratio of chlorine to paraffin.

CH4 + Cl2 ⇒ CH3Cl + HCl

                     Methyl chloride

Direct chlorination occurs by free radical mechanism as explained in general organic chemistry.

Bromination takes place with greater difficulty than chlorination and there is fewer tendencies for polysubstitution. Bromination is more selective, i.e bromine has a much greater tendency than chlorine to replace tertiary hydrogen in preference to secondary or primary.

Direct chlorination of alkanes may be effected by means of sulphonyl chloride in presence of light and a trace of an organic peroxide.

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