Reaction of Toluene with Chlorine

This is a quite interesting reaction because depending upon conditions of reaction (whether there’s sunlight present or not) reactants Toluene and Chlorine will react with each other through different mechanisms. Therefore producing different products.

Just to be clear, if your already not aware of what’s Toluene, it’s another name of methylbenzene (CH3 – C6H6) which have structure as in below diagram.

Toluene or MethylBenzene Structure

Let’s now have a look at reactions.

Reaction of Toluene with Chlorine in absence of light

If Toluene and Chlorine reacts with each other in absence of light then electrophilic aromatic substitution reaction will take place and as methyl group is ortho or para directing therefore chlorine atom will either attach to carbon position next to methyl group on benzene ring or at position opposite to it.
This will yield a mixture of 1-chloro-2-methylbenzene and 1-chloro-4-methylbenzene.

Below diagram shows the process of this reaction.

Reaction of Toluene with Chlorine in absence of light mechanism explained

Reaction of Toluene with Chlorine in presence of light

If Toluene and Chlorine reacts with each other in presence of light then free radical substitution reaction will take place. This reaction will remove H atoms from methyl group and replace them with Cl atoms. Depending upon quantity of chlorine available for reaction different products will be formed.

If quantity of chlorine available is less then chloromethylbenzene will be produced
But if chlorine is available in excess amount then trichloromethylbenzene will be produced

Therefore reaction of Toluene with Chlorine in presence of light will produce either chloromethylbenzene or tricholorometylbenzene depending upon quantity of chlorine available for reaction.

Below diagram shows the process of this reaction.

Reaction of Toluene with Chlorine in presence of light mechanism

Summary

If Toluene reacts with Chlorine in presence of light then chloromethylbenzene or trichloromethylbenzene will be formed depending upon amount of chlorine available. On the other hand, if Toluene reacts with Chlorine in absence of light then either 1-chloro-2-methylbenzene or 1-chloro-4-methylbenzene will be formed.

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