Haloalkanes and Haloarenes

Introduction

Are you aware that haloalkanes and haloarenes can be found in the environment? During the Vietnam War, haloarenes were employed as herbicides to defoliate the jungles and make it simpler to battle. Microorganisms such as bacteria are unable to break down these haloarenes. As a result, it has remained unaltered in the rainforest soils to this day.Are you aware that haloalkanes containing halogens such as chlorine, bromine, and iodine pose a threat to the ozone layer in the atmosphere? Chlorofluorocarbon is one of the most frequent haloalkane compounds that contribute to ozone depletion. We may have come across haloalkanes and haloarenes in our daily lives as well as in enterprises for a variety of purposes. Please enlighten us on these organic substances.

Haloalkanes and Haloarenes 

There are two types of haloalkanes and haloarenes.

Haloalkanes and haloarenes are formed when a hydrogen atom in an aliphatic or aromatic hydrocarbon is replaced by halogen atoms. The chemical generated when a hydrogen atom from an aliphatic hydrocarbon is replaced by a halogen atom is known as haloalkane. Alkyl halide and haloalkane are other names for it.

When a hydrogen atom from an aromatic hydrocarbon is substituted with a halogen atom, the resulting chemical is known as haloarene. Aryl halide or halogenarene are other names for it. The halogen group is represented by X in a haloalkane (R – X). The halogen is connected to an sp3 hybridised atom of an alkyl group, whereas the halogen is attached to a sp2 hybridised atom of an aryl group in haloarene (Ar – X).

Ethyl bromide CH3CH2 Br is an example of a haloalkane (sp3C)

Bromobenzene (C6H5Br) is an example of a haloarenes (sp2C)

Haloalkanes and haloarenes are distinguished by the fact that haloalkanes are made from open-chain hydrocarbons (alkanes), whereas haloarenes are made from aromatic hydrocarbons (it is a type of hydrocarbon that forms a circular structure or ring-like structure due to sigma bonds and delocalized pi electrons between carbon atoms)

Haloalkanes 

Haloalkanes are organic chemical compounds in which one or more hydrogen atoms from an alkane group are replaced with a halogen group (elements of group 17 such as chlorine, bromine, Fluorine, iodine, etc.).

Haloalkanes are saturated organic compounds in which the halogen atom is bonded to a single carbon atom and all chemical linkages are single bonds.

Haloarenes

Aryl Halides/Haloarenes/Halogenoarene are aromatic compounds in which a halogen group replaces one or more hydrogen atoms linked to an aromatic ring. Haloarenes differ from haloalkanes primarily in their manufacturing technique and characteristics. This class of chemical and its derivatives has a wide range of applications. Aryl chlorides are one of the most important members of the haloarene class.

Classification of Haloalkanes and Haloarenes:

They can be classified  based on the following criteria:

The number of hydrogen atoms in a molecule

• sp3 C—X Bonded Compounds
• The sp2 C-X Bond is found in compounds.

1) The total number of hydrogen atoms in the universe

Haloalkanes and haloarenes can be classified as mono, di, or poly (tri, tetra, and so on) compounds based on the number of hydrogen atoms. It gets its name from the number of halogen atoms that these compounds have in their structure.

On the basis of the hybridization of the carbon atom to which the halogen atom is bonded, mono halo compounds can be divided into classes and subclasses.

2) sp3 C—X Bonded Compounds [In this case, X (Halogen Group) equals F, Cl, Br, and I]

These substances are further split into three categories. They are as follows:

Haloalkanes/Alkyl Halides (R–X)

The halogen atom is connected to an alkyl group in this class. This class follows the generic homologous formula CnH2n+1 X. They are further divided into primary, secondary, and tertiary varieties based on the carbon atom to which the carbon carrying halogen (X) atom is linked. The type of the carbon atom to which the halogen is bonded determines this classification.

Alkyl-Halide and Haloalkanes Classification

Allylic Halides 

The bonding of a halogen group with an sp3 hybridised carbon atom present adjacent to a carbon-carbon double bond structure (C=C) forms this classification of compounds. Allylic carbon refers to a carbon-carbon double bond structure. As a result, the name allylic halides was coined.

Example of Allylic Halides: haloalkanes

Benzylic Halides 

When a halogen atom is bonded to an sp3 hybridised carbon atom, this type of chemical is created. To produce benzyl halides, the sp3 hybridised carbon atom must be present close to an aromatic ring.

Examples of Benzylic Halides 

3) Compounds that have a sp2 C-X bond

Vinyl halides and aryl halides are examples of this type of chemical.

Vinyl Halides I

When a halogen atom is coupled to a sp2 hybridised carbon atom that is present next to a carbon-carbon double bond (C=C), these compounds are produced.

Aryl Halides 

When the halogen group is attached to an aromatic ring’s sp2-hybridised carbon atom, this family of compounds is generated.

Uses of haloalkanes and haloarenes

Haloalkanes and Haloarenes are used in a variety of applications which are as follows-:

1.Haloalkanes and haloarenes are employed in a variety of industrial and everyday applications.

2.They’re employed in a variety of applications, including flame retardants, propellants, solvents, medicines, refrigerants, and fire extinguishants.

3.They are utilised as non-polar chemical solvents.

4.These chemicals’ derivatives are employed in medicine, for example, chloramphenicol, which is used to treat typhoid fever.

5.Malaria patients are treated with synthetic halogen compounds like chloroquine.

6.Insecticides containing DDT are used.

Environmental Consequences

These chemicals are widely used in commercial applications. Halocarbons, on the other hand, have been connected to major pollutants and chemicals that are harmful to the environment. One of the major causes of ozone depletion in the atmosphere is the common molecule CFC (chlorofluorocarbon). Methyl bromide is another hotly debated fumigant that has been connected to a slew of negative environmental impacts. These chemicals have repeatedly been shown to be a substantial environmental hazard due to their detrimental effects.

However, some chemicals, such as methyl iodide, do not deplete the ozone layer in the atmosphere. Furthermore, the molecule has been classified as a non-ozone layer depleting substance by the USEPA (United States Environmental Protection Agency).

Conclusion  

We can deduce that haloalkanes are alkanes that have had at least one hydrogen replaced with halogen. Haloalkanes are aliphatic compounds, whereas haloarenes are aromatic compounds. These chemicals are useful in both therapeutic and industrial settings. In comparison to alkanes, haloalkanes have a higher boiling and melting point.