Haloalkanes and Haloarenes
Stuid
Haloalkanes and haloarenes are present in our environment. For example, it is said that haloarenes were used as herbicides in the Vietnam war. It helped in defoliating the jungles, thus making it easier to fight in the war. Haloarenes can neither be decomposed nor broken down by microorganisms.
- Haloalkanes (halogens like chlorine and bromine) are a threat to the ozone layer.
- Both haloalkanes and haloarenes have several industrial applications.
Haloalkane and haloarene compounds are formed when a hydrogen atom in an aliphatic or aromatic hydrocarbon is replaced by halogen atoms.
- The major difference between haloalkanes and haloarenes is that while haloalkanes are obtained from open-chain hydrocarbons/haloarenes are derived from aromatic hydrocarbons.
- Haloalkanes are saturated organic compounds. The chemical bonds are attached to the carbon atom in single bonds. The halogen atom gets attached to a single carbon atom.
- Haloarenes are different from haloalkanes in their method of preparation and their properties. The class compound and its derivatives are used for various purposes. Aryl chlorides are one of the most important members of the haloarene class.
Number of Hydrogen atoms
Haloalkanes/Haloarenes can be divided into mono, di, or poly on the basis of the number of hydrogen. They are named on the basis of the number of halogen atoms they contain in their structures.
Based on the hybridization of the carbon atom to which the halogen atom is attached, mono halo compounds are divided into classes and subclasses.
Compounds with sp3 C—X Bond
They can be further classified into three types.
i) Alkyl Halides/Haloalkanes (R – X)
- The Halogen atom gets attached to the alkyl group.
- CnH2n+1 X is the homologous formula followed by the class.
- They are further classified into primary, secondary, and tertiary, on the basis of the carbon atom to which the carbon bearing halogen (X) atom is bonded.
- The differentiation is basically based on the nature of the carbon atom to which the halogen is attached.
ii) Allylic Halides
- Formed due to the bonding of halogen groups possessing sp3 hybridized carbon atoms, which are present next to a carbon-carbon double bond structure.
iii) Benzylic Halides
- Such compounds are formed when a halogen atom gets attached to an sp3 hybridized carbon atom.
- The hybridized carbon atom shall be present next to the aromatic ring for forming benzyl halides.
Compounds Having the sp2C-X Bond
Classes of compounds include vinyl halides and aryl halides.
i) Vinyl Halides
Such compounds are formed when a halogen atom is attached to sp2 hybridized carbon that is present next to a carbon-carbon double bond (C=C).
ii) Aryl Halides
Aryl halides are formed when the halogen group is bonded to an sp2 hybridized atom of carbon in an aromatic ring.
Applications
Haloalkanes and haloarenes find their application in several industrial and day to day purposes. They are used as flame retardants, propellants, solvents etc ..
Apart from being used as solvents for non-polar compounds, derivatives of these compounds are used for medicinal properties like in the treatment of typhoid (chloramphenicol).
‘Chloroquine’ is used for the treatment of malaria.
DDT is used as an insecticide.
Environmental Effects
These compounds are used for a wide variety of commercial purposes. Halocarbons are associated with pollutants and toxins which adversely affect the environment.
CFC (chlorofluorocarbon) is primarily responsible for ozone layer depletion. Methyl bromide fumigant has several adverse impacts on the environment as well.
On the other hand, compounds such as Methyl iodide do not cause any harm to the ozone layer.
In this article, we have discussed haloalkanes and haloarenes in detail.
Answer) Haloarenes.
Answer) Chloroquine.
Answer) Chlorofluorocarbon.