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.

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Overview ofย Haloalkanes and Haloarenes

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, In haloalkanes, the halogen atoms are attached to sp3 hybridized carbon atoms whereas in haloarenes, the point of attachment is sp2 hybridized carbon atom. The difference in the hybridization state of the carbon atom in C-X bond is responsible for the different characteristics which the two families have.ย The presence of halogens makes 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:

  1. Number of halogen atoms in the molecule
  2. sp3 hybridized carbon-halogen bond.
  3. 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 a sp2 hybridized carbon Vinyl Halide The halogen atom is attached to C=C (sp2 hybridized carbon).
Aryl Halide The halogen is attached to a 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.

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Uses of Haloalkanes and Haloarenes

Some 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 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 labelled 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 BYJUโ€™S and download the mobile application on your smartphone.

Frequently Asked Questions-FAQs


1. What is the difference between haloalkanes and Haloarenes?

When hydrogen atoms in aliphatic hydrocarbons(alkanes) are replaced by halogen atoms ,the compounds formed are known as haloalkanes. Similarly, when hydrogen atoms attached to benzene rings are replaced by halogen atoms the compounds that are formed are known as haloarenes.


2. What are haloalkanes reactions?

Haloalkanes react with magnesium metal in the presence of completely anhydrous ether to form organomagnesium halide which is popularly known as Grignard reagents. Haloalkane undergoes nucleophilic substitution reaction by the presence of aqueous alkali solution or moist silver oxide solution form alcohols.


3. Which is the example of Haloarenes?

When hydrogen atoms attached to benzene rings are replaced by halogen atoms the compounds that are formed are known as haloarenes. Examples of haloarenes are chlorobenzene, bromobenzene, iodobenzene, 2-Chlorotoluene etc.


4. What are the uses of Haloarenes?

Haloarenes used to prepare several compounds like DDT, Picric acid, Phenol etc. DDT was used as insecticide to destroy anopheles mosquitoes which spread malaria but due to its toxic nature it was banned in the year 1973. Picric acid is used in the production of explosives, matches, electric batteries, manufacturing colored glass and synthesis of dyes. Phenol is used in the manufacture of nylon and other synthetic fibers.


5. What is Mono Haloalkanes?

The haloalkane which contains only one halogen atom is known as mono haloalkane

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