The nature of the product depends on the reaction conditions and the types of reaction mechanism.
Relative Reactivities of the Chlorinated Products
Chloromethylbenzene behaves as a normal (aliphatic) haloalkane.
It readily undergoes nucleophilic substitution reactions, due to the polar bond.
is much less reactive towards nucleophiles because the Cl is attached to an aromatic ring.
The C-Cl bond can be shown to be stronger (bond length 0.169nm compared to 0.177nm in a haloalkane), which indicates that it is less polar.
This is because the electrons are drawn towards the electron deficient C atom so that they partially neutralise the charge.
The charge is delocalised over the ring.
The electrophilic substitution is only possible in the laboratory if other electron withdrawing groups are present:
The NO2 groups make the C atom more
- Bothand will give electrophilic substitution reactions in the benzene ring.
is less reactive since Cl withdraws electrons from the ring making them less available to electrophiles.
Unlike alkenes, benzene is not oxidised by KMnO4 and will not decolourise it. This is due to the extra stability of benzene arising from delocalisation that makes it resistant to addition.
Methylbenzene is oxidised by boiling with acidified KMnO4 and will therefore decolourise it. It is the CH3 group that is oxidised.