A Quick Note on Compounds of Halogens

The elements chlorine, fluorine, iodine, bromine, and astatine (the radioactive element) are together known as halogens. The chemical and physical properties of these elements have been studied carefully. These compounds reveal a perfect gradation, and they belong to group Vll in the periodic table. In this article, you can read a quick note on compounds of halogens.

Halogen Compounds

One of the permanent properties of halogens is that they are highly reactive. Due to this nature, they can form various compounds, for instance, interhalogen compounds, halogenated/organohalogen compounds, and polyhalogenated compounds. A brief discussion regarding these compounds of halogens is mentioned below:

Interhalogen Compounds

This is a molecule compound that belongs to two or more separate atoms of halogen, namely chlorine, fluorine, iodine, bromine, and astatine and there are no atoms from any other group of elements. Interhalogen compounds are formed during that time when the group elements of the halogen family react with each other. All the interhalogen compounds are binary. This compound can be expressed as XYn,  where n = 1, 3, 5 and 7. X is a halogen and is less electronegative than other Y halogens. Y is a more electronegative halogen. Because of the odd valencies of the halogen, the value of ‘n’ is also odd. These halogens need to undergo hydrolysis and are ionised for creating polyhalogen ions. The polyhydrogen is formed from astatine and has a very short half-life because astatine is highly radioactive.  The four forms of interhalogen compounds are the following:

• Tetratomic interhalogens (AX3)
• Diatomical interhalogens (AX)
• Octatomical interhalogens (AX7)
• Hexatomical interhalogens (AX5)

Halogenated/Organohalogen Compounds

Halogenated/organohalogen compounds are a type of organic compound that belongs to only one halogen which is bonded to carbon. These compounds are subdivided into vinylic, alkyl, acyl halide, and aryl. Halogenated/organohalogen compounds differ widely in chemical reactivity that depends on the halogen and their class. They may even differ within a class. These organohalogen compounds are essential industrial chemicals. They are usually used as pesticides and solvents and are also useful in preparing drugs, dyes and synthetic polymers. However, more than 2000 organohalogen compounds are recognised as naturally occurring materials produced by different fungi, plants, marine organisms, and bacteria. The halogens in the organic molecules are introduced by various available synthetic methods. Similarly, the organohalogen compounds can be converted to the other functional group of classes by using the reliable method.

Polyhalogenated Compounds

We all are aware of the common pesticide called DDT.  This DDT is nothing but one of the usual polyhalogenated compounds. These compounds have various uses. These are carbon compounds consisting of more than one halogen atom. Polyhalogenated compounds are commonly used in industrial sectors and agriculture. Moreover, they are used for various purposes, for instance, anaesthetics, pesticides, and solvents. Some important polyhalogenated compounds are chloroform, methylene chloride, iodoform, carbon tetrachloride, benzene hexachloride, DDT, etc. 

1. Chloroform (Trichloromethane)

Chloroform is a colourless polyhalogenated compound available in liquid form. It is also known as trichloromethane and has a sweet smell. The boiling point of chloroform is 334 K. It can be slowly oxidised by air and forms a poisonous gas named ‘phosgene’ in the presence of light. Hence, it is crucial to store the bottles of chloroform away from the sunlight.

2.Methylene chloride (Dichloromethane)

This polyhalogenated compound is present in the form of a solvent. Dichloromethane, also known as methylene chloride, can be used for various purposes, such as drug manufacturing, paint removal, cleaning solvent, and as a propellant in aerosols.

3.Iodoform (Triiodomethane)

Iodoform’s IUPAC name is triiodomethane. It has a distinct smell and is a pale yellow colour solid. Previously, the polyhalogen compound was used as an antiseptic as it releases free iodine more than iodoform, resulting in a pungent odour. Hence, presently, other iodine-containing formulations are used as antiseptics.

4.DDT (p,p´-Dichlorodiphenyltrichloroethane)

DDT is available in various forms such as powder, granules, aerosols, etc. DDT was named the first organic insecticide with chlorine.

Conclusion

The elements chlorine, fluorine, iodine, bromine, and astatine (the radioactive element) are  known as halogens. The chemical and physical properties of these elements have been studied carefully and they showed a perfect gradation. They belong to group Vll in the periodic table. One of the permanent properties of halogens is that they are highly reactive. Thus, they can form various compounds. The main three compounds of halogen are interhalogen, halogenated/organohalogen, and polyhalogenated compounds.