How do you account for the formation of ethane during chlorination of methane?


Chlorination of methane takes place following a free radical chain mechanism. The whole reaction mechanism can be represented by the following three steps below: -


Step 1: Initiation:


The reaction begins with the homolytic cleavage of Cl – Cl bond as:



Step 2: Propagation:


In the second step, chlorine free radicals attack the methane molecules and break down the C–H bond to generate methyl radicals as:-



These methyl radicals react with other chlorine free radicals to form methyl chloride along with the liberation of a chlorine free radical.



Hence, methyl free radicals and chlorine free radicals set up a chain reaction. While HCl and CH3Cl are the major products formed, other higher halogenated compounds are also formed as:-



Step 3: Termination:


Formation of ethane is a result of the termination of chain reactions taking place as a result of the consumption of reactants as:-



Hence, by this process, ethane is obtained as a by-product of chlorination of methane.


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