Haloarenes

Haloarene is a halogenated aromatic hydrocarbon formed when a halogen atom replaces an aromatic hydrocarbon’s hydrogen atom. Haloarenes were employed as herbicides during the Vietnam War to defoliate jungles and simplify soldiers’ battles. Bacteria cannot eat and degrade these haloarenes. Consequently, it has continued to exist in its native state in rainforest soils until today. Haloalkanes, which include halogens such as chlorine, bromine, and iodine, deplete the ozone layer on the Earth. Chlorofluorocarbon is a hazardous haloalkane that contributes to the loss of the ozone layer. Haloalkanes and haloarenes are organic compounds we encounter daily and in several industrial applications.

Haloalkanes and Haloarenes

Haloalkanes and haloarenes are organic compounds formed when hydrogen atoms in an aliphatic or aromatic hydrocarbon are swapped with halogen atoms from another atom. A haloalkane molecule is formed when another replaces one hydrogen atom in an aliphatic hydrocarbon. These words are synonymous with alkyl halide and haloalkane. Haloarene is a halogenated aromatic hydrocarbon formed when a halogen atom replaces an aromatic hydrocarbon’s hydrogen atom. In certain areas, it is also referred to as aryl halide or halogenoarene. Haloalkanes (R – X) are alkenes with the halogen group denoted by X. In contrast to haloarene (Ar– X), which is bonded to an aryl group rather than an alkyl group, haloarene (Ar– X) is attached to an sp3 hybridised alkyl group. Haloarene examples are chlorobenzene, bromobenzene, iodobenzene, 2-Chlorotoluene etc. Haloalkanes are organic chemical compounds generated when one or more hydrogen atoms from an alkane group are substituted with one or more halogen atoms from a halogen group (elements of group 17 such as chlorine, bromine, Fluorine, iodine, etc.). To summarise, haloalkanes are saturated organic molecules that include halogen and carbon atoms and have single bonds connecting them to the carbon atom. A halogen group is often substituted for one or more hydrogen atoms in aromatic compounds having one or more hydrogen atoms and an aromatic ring. Aryl halides/haloarenes/halogenoarene refers to aromatic compounds with one or more hydrogen atoms linked to an aromatic ring. The synthesis procedure and the resulting characteristics distinguish haloarenes from haloalkanes.

Haloalkanes and Haloarenes: Chemical Properties

Haloalkanes and haloarenes have the following characteristics:

• Contain Hydrogen Atoms

According to the number of hydrogen atoms present, they are classified as mono, di, or poly (tri, tetra, and so on) haloalkanes and haloarenes compounds. The word “halogenated” refers to the presence of halogen atoms in the structures of these substances as an illustration.

• Compounds containing a C—X bond of type sp³

Each of these chemicals may be classified further into one of three categories. Their given names are as follows:

1. The halogen atom is covalently attached to an alkyl group in this family of molecules.
2. The most often seen homologous formula for this class is C_nH_2n+1 X. Additionally, they are categorised as primary, secondary, or tertiary carbon atoms based on the carbon atom to which the halogen (X) atom is attached.
3. The chemical composition of the carbon atom to which the halogen is attached determines the element’s categorisation.

• Halides of Allylic Acid

A carbon-carbon double bond structure (C=C) is formed when halogen groups containing an sp³ hybridised carbon atom are joined together, a carbon-carbon double bond structure (C=C) is formed. Allylic carbon refers to the double bond formed between carbon and carbon. As a result, they are referred to as allylic halides.

• Compounds were having an sp²C-X kind of link.

When a halogen atom reacts with a sp2 hybridised carbon atom near a carbon-carbon double bond (C=C), these compounds are generated.

• Halides of Compounds

Chlor Halogen compounds are generated when a halogen group forms a covalent link with an aromatic ring’s hybridised sp² carbon atom.

Haloalkanes and haloarenes: Applications

• Haloalkanes and haloarenes are commonly employed in industrial and residential applications. They are utilised as flame retardants, fuels, solvents, medicines, refrigerants, and fire extinguishers.
• The derivatives of these substances have therapeutic properties; for example, chlorine is used to treat typhoid fever and other ailments.
• Synthetic halogen compounds developed from naturally occurring halogen compounds, such as chloroquine, are administered to malaria sufferers.
• DDT is an insecticide.

Environmental Consequences

These compounds are often used in the commercial sector for various reasons. Conversely, halocarbons have been connected to multiple environmental contaminants and poisons. For example, the widely used chemical molecule CFC (chlorofluorocarbon) contributes significantly to ozone depletion in the environment. Methyl bromide is another contentious fumigant that has been associated with a variety of adverse environmental impacts. Due to their detrimental impacts on the ecosystem, these chemicals have repeatedly been singled out as a key source of concern for environmental preservation.

Reactions of Nucleophilic Substitution

Nucleophilic substitution reactions occur in the presence of haloarenes. These alkanes are much less reactive than haloalkanes in the presence of nucleophilic substitution.

Conclusion

During the Vietnam War, haloarenes were used as herbicides to defoliate the jungles. Microorganisms such as bacteria are unable to break down these haloarenes. As a result, it has remained unaltered in the rainforest soils. Hydrocarbons having one or more hydrogen atoms substituted by halogen atoms are haloalkanes and haloarenes. Haloalkanes and haloarenes are distinguished because haloalkanes are formed from open-chain hydrocarbons (alkanes), whereas haloarenes are derived from aromatic hydrocarbons.