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Chemical Properties of Haloarenes

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Haloarenes, also known as aryl halides, undergo a number of reactions such as nucleophilic substitution reactions, electrophilic substitution reactions. Like haloalkanes, they also react with metals. Let us discuss them one by one :

Nucleophilic Substitution Reactions in Haloarenes

Haloarenes undergo nucleophilic substitution reactions. They are, however, far less reactive than haloalkanes towards nucleophilic substitution reactions.

Why are haloarenes less reactive towards nucleophilic substitution reactions?

Haloarenes are far less reactive than haloalkanes towards nucleophilic substitution reactions due to the following reasons :

Out of chlorobenzene and chloromethane which is more reactive towards nucleophilic substitution reaction?

Electrophilic Substitution Reactions of Haloarenes

Electrophilic substitution reactions are prevalent in aromatic compounds, and, haloarenes are no exception. Halogen atom is slightly deactivating and o,p-directing; therefore, electrophilic substitution in haloarenes occurs at ortho and para positions with respect to the halogen atom.

Why are halogens deactivating?

Due to −I-effect, halogen atoms have some tendency to withdraw electrons from the benzene ring that reduces the overall electron density on the ring. As a result, the ring gets somewhat deactivated as compared to benzene.

Why does substitution occur only at ortho and para positions of haloarenes?

In haloarenes, electron density is more at ortho and para positions which is evident from the resonance structures of haloarenes given below :

Resonance effect in haloarenes : -ve charge at orhto and para

Because of this reason, electrophiles (electron deficient species) get attracted towards ortho and para positions of haloarenes.

Electrophiles get attracted to ortho and para positions

Negative charge at ortho position of haloarene attacks on electrophile
Negative charge at para position of haloarene attacks on electrophile

Reaction of Haloarenes with Metals

Aryl halides, like alkyl halides, react with metals to form a number of compounds.

We will learn more about nucleophilic substitution, electrophilic substitution and reaction with metals in case of haloarenes on next three pages.

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