Chemistry > Alkyl Halides and Aryl Halides > 11.0 Aryl Halides
Alkyl Halides and Aryl Halides
1.0 Alkyl halides
2.0 Halogen Derivatives of Unsaturated Hydrocarbons
3.0 Nomenclature
4.0 Isomerism
5.0 Nature of $C- X$ bond
6.0 Preparation
7.0 Physical Properties
8.0 Chemical Properties
9.0 Elimination Reactions
10.0 Reaction with Metals
11.0 Aryl Halides
12.0 Chemical Properties of Aryl Halides
13.0 Halogenation
14.0 Sulphonation
15.0 Nitration
16.0 Friedel-Craft's alkylation
17.0 Friedel Craft's acylation
11.1 Preparation of Aryl Halides
From benzene:
- Benzene reacts with chlorine to form chlorobenzene in the presence of a Lewis acid ($FeCl_3$ or $AlCl_3$). Under similar conditions, bromobenzene can also be formed.
- Reaction of benzene with iodine is reversible and HI formed should be immediately oxidised using $HNO_3$ or periodic acid.
- Chlorination of toluene in dark in the presence of iron or ferric chloride gives a mixture of orthochlorotoluene and parachlorotoluene. The separation of this mixture is possible due to the difference in the melting points of the isomeric chlorotoluenes.
From diazonium compounds:
- Sandmeyer's reaction: Benzene diazonium chloride, obtained from aniline, is heated with cuprous chloride in presence of $HCl$ to form chlorobenze. Similarly, bromobenzene can also be formed.
- If $Cu$ powder is used instead of cuprous chloride, the reaction which occurs is Gattermann reaction.
- Iodobenzene can be obtained by warming of benzene diazonium salt with $KI$.
- Fluorobenzene can be obtained by the reaction of benzene diazonium chloride with fluoboric acid, followed by heating the diazonium fluoborate salt.
