Question

Explain the mechanism of chlorination of methane?

Answer 1

If a mixture of methane and chlorine is exposed to a flame, it explodes - producing carbon and hydrogen chloride. This is not a very useful reaction! The reaction we are going to explore is a more gentle one between methane and chlorine in the presence of ultraviolet light - typically sunlight. This is a good example of a photochemical reaction - a reaction brought about by light.

CH4+Cl2→CH3Cl+HCl
CH4+Cl2→CH3Cl+HCl
The organic product is chloromethane. One of the hydrogen atoms in the methane has been replaced by a chlorine atom, so this is a substitution reaction. However, the reaction doesn't stop there, and all the hydrogens in the methane can in turn be replaced by chlorine atoms. Multiple substitution is dealt with on a separate page, and you will find a link to that at the bottom of this page.

The mechanism
The mechanism involves a chain reaction. During a chain reaction, for every reactive species you start off with, a new one is generated at the end - and this keeps the process going. The over-all process is known as free radical substitution, or as a free radical chain reaction.

Chain initiation: The chain is initiated (started) by UV light breaking a chlorine molecule into free radicals.
Cl2 →→ 2Cl

Chain propagation reactions : These are the reactions which keep the chain going.
CH4 + Cl→→CH3 + HCl

CH3 + Cl2→→CH3Cl + Cl

Chain termination reactions: These are reactions which remove free radicals from the system without replacing them by new ones.
2Cl→→Cl2

CH3 + Cl →→ CH3C l

CH3 + CH3→→CH3CH3

Answer 2

Clorination of methane -

Methane and Chlorine gases reacts with each other at the temperature of

250° C to 400°C in presence of ultraviolet light and form mainly methyl chloride (chloromethane) and

hydrogen chloride. This reaction is called Chlorination of methane

Chemical reaction -

CH4 + CL2 ------:(light)---> CH3CL + HCL.

I hope it will really help you !!!