Name: Nomenclature of Haloalkanes and Haloarenes
Uploaded: 2019-07-19
Duration: 9 min 1 s
Description: Haloalkanes are formed by replacing a hydrogen atom in an alkane with a halogen atom. Haloarenes are derived by replacing the hydrogen atom attached to the b...

Question

Discuss the resonating structures of chlorobenzene. How do you account for double bond character of C-Cl bond? Describe the industrial method of preparation of chlorobenzene?

Accepted Answer

Chlorobenzene is to be regarded as resonance hybrid of the following contributing forms as shown below:

There is a negative charge at ortho and para positions. Thus, electron density increases at these positions. Thus, chlorine present in chlorobenzene is ortho and para directing. So, electrophile will attack at these positions in chlorobenzene.

In haloarenes, the lone pairs of electrons on the halogen atom are delocalized on the benzene ring due to resonance effect. As a result, C-X bond acquires some double bond character. Thus, in chlorobenzene, C-Cl bond acquires double bond character.

Industrial method of preparation of chlorobenzene:

Chlorobenzene is prepared commercially by the Raschig process. In this process, a mixture of benzene vapours, air and hydrogen chloride is passed over heated cupric chloride to produce chlorobenzene.

$2 C_{6} H_{6} + 2 HCl + O_{2} \overset{{CuCl}_{2} + ∆}{\to} 2 C_{6} H_{5} Cl + 2 H_{2} O$

Discuss the resonating structures of chlorobenzene. How do you account for double bond character of C-Cl bond? Describe the industrial method of preparation of chlorobenzene?

Important Questions on Haloarenes (Aryl Halides)

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