Haloalkanes And Haloarenes

What are Haloalkanes and Haloarenes?

Haloalkanes and haloarenes are the hydrocarbons in which one or more hydrogen atoms have been replaced with halogen atoms. The primary difference between haloalkanes and haloarenes is that haloalkanes are derived from open-chain hydrocarbons (alkanes) whereas haloarenes are derived from aromatic hydrocarbons.

Haloalkanes are commonly referred to as alkyl halides whereas haloarenes are commonly referred to as aryl halides. These compounds can contain multiple halogen atoms, as illustrated below.

Haloalkanes and Haloarenes

Generally, the halogens are attached to sp3 hybridized carbon atoms in these compounds. The presence of halogens make haloalkanes and haloarenes more chemically reactive than the parent alkanes and aromatic compounds. These compounds have many medicinal uses as well.

Classification of Haloalkanes and Haloarenes

Alkyl halides and aryl halides can be classified based on the following parameters:

  • Number of halogen atoms in the molecule
  • sp3 hybridized carbon-halogen bond.
  • sp2 hybridized carbon-halogen bond.

The classification of haloalkanes and haloarenes is described in the tabular column provided below.

Classification based on the number of halogen atoms. Monohaloalkanes and Monohaloarenes Contain 1 halogen atom
Dihaloalkanes and Dihaloarenes 2 halogen atoms are attached
Trihaloalkanes and Trihaloarenes Contain 3 halogen atoms
Haloalkanes and haloarenes in which the halogen is attached to an sp3 hybridized carbon. Alkyl Halide Halogen is attached to an alkyl chain.
Allylic Halide The halogen atom is attached to an sp3 hybridized carbon which is adjacent to C=C (double bond or sp2 hybridized carbon)
Benzylic Halide The halogen is attached to an sp3 hybridized carbon which is attached to a benzene ring.
Compounds in which the halogen is attached to an sp2 hybridized carbon Vinyl Halide The halogen atom is attached to C=C (sp2 hybridized carbon).
Aryl Halide The halogen is attached to an sp2 hybridized carbon which belongs to an aromatic ring.

Thus, the different ways in which haloalkanes and haloarenes are classified are discussed with the help of a tabular column. Click here to learn about the nomenclature of haloalkanes as per IUPAC guidelines.

Uses of Haloalkanes and Haloarenes

Some of the important applications of these compounds are listed below.

  • These organic compounds can dissolve non-polar compounds and are therefore used as solvents.
  • Many derivatives of alkyl and aryl halides are used in medicine. One such example is the compound chloramphenicol, which is used to treat cases of typhoid.
  • Another such example is chloroquine, which is very useful in the treatment of malaria.
  • Dichlorodiphenyltrichloroethane (commonly referred to as DDT) is used as an insecticide.

Some haloalkanes and haloarenes have adverse effects on the environment and are labeled as pollutants. One such example is chlorofluorocarbons (or CFCs), which lead to the depletion of the ozone layer which protects the Earth from the harmful radiation coming from the sun. To learn more about these compounds, register with BYJU’S and download the mobile application on your smartphone.


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Chlorination of toluene in presence of light and heat followed by treatment with aqueous NaOH gives