Classification of Organic Halogen Compounds.

Organic halogen compounds are organic compounds that contain a single or more atom of hydrogen altered by an equivalent number of halogen atoms (F, Cl, Br, or I). Halogen atoms can be found in almost any type of organic substance (e.g., alcohols, ketones, and carboxylic acids).

Haloalkanes, commonly called alkyl halides, are a class of chemical compounds made up of an alkane with one or more hydrogen atoms substituted by a halogen atom. The number of carbons bound to the carbon-containing halide determine the classification of halogen derivatives.

The halogen atom is connected to an allylic carbon atom which is sp3-hybridised beside a carbon-carbon double bond (C=C) in these compounds. The halogen atom is attached to an sp3 hybridised. A carbon atom is located next to an aromatic ring in these compounds.

Classification of Halogen Compounds

The classification of halogen compounds is based on two criteria.

1) According to the number of halogens

2) According to hybridisation of carbon attached with halogen

On the basis of number of halogens

1. a) Mono Halo compounds
2. b) Poly Halo compounds 

On the basis of hybridisation of carbon attached with halogen

1. a) Compounds containing Csp3 – X bond

Alkyl halides (or) haloalkanes CH3 iodomethane

Allylic halides CH2=CH-CH2-Cl Allyl chloride

Benzylic halides C6H5CH2-Br Benzyl bromide

Alicyclic halides Br bromo cyclobutane

1. b) Compounds containing Csp2 – X bond

Vinylic halides CH2 = CHI vinyl iodide

Aryl halides C6H5 Cl chlorobenzene

Classification of Halogen Derivatives

Aromatic halogen compounds are arenes’ halogen derivatives. The derivative is obtained when a hydrogen atom in a side chain connected to an aromatic ring is substituted by a halogen atom, known as a side chain derivative. The aryl derivatives of haloalkane are the side chain halogen derivatives.

Halogen derivatives are compounds made from hydrocarbons by replacing one or more H-atoms with the same number of halogen atoms.

Based on the type of the hydrocarbon remnant whereby the halogen atom is linked, the classification of halogen derivatives are neatly grouped into three classes:

• Alkyl halides 
• Aryl halides 
• Alkenyl halides 

Alkyl halides are compounds wherein the halogen atom is linked to an alkyl or a derived alkyl group. Aryl halides are compounds where one of the aromatic ring’s hydrogens is swapped by a halogen atom. Finally, alkenyl halides are compounds in which a halogen atom is connected to a carbon atom linked to another carbon atom by a double bond.

According to the number of halogen atoms in the molecule, halogen derivatives might be mono-, di-, tri-, or tetra-. 

Classification of Halogen Derivatives of Alkanes

Halogen derivatives are compounds made from hydrocarbons by replacing one or even more hydrogen atoms with the same number of halogen atoms. The classification of halogen derivatives of hydrocarbons can be divided into three categories:

• Halo-alkanes are halogen derivatives of saturated hydrocarbons (Alkanes).
• Halogen derivatives of unsaturated hydrocarbons (Alkenes and alkynes)-Halo-alkene or Halo-alkyne or Halo-alkyne or Halo-alkyne or Halo-alkyne or Halo-alkyne
• Halo-arenes are halogen derivatives of aromatic hydrocarbons (Arenes).

Classification of Halogen Derivatives of Alkyl Halides

The bonding arrangements of the atoms involved are used to classify functional groups. Halogens only have one neutral bonding pattern. Hence, their categorisation cannot be determined by them.

• Halides of primary alkyls

The carbon carrying the halogen atom is only connected to one other alkyl group in a primary (1°) halogenoalkane.

• Secondary alkyl halides are a type of secondary alkyl halide

The carbon attached halogen is connected directly to two other alkyl groups, which could be the same or different, in a secondary (2°) halogenoalkane.

• Halides of tertiary alkyls

The carbon atom carrying the halogen is directly connected to three alkyl groups in a tertiary (3°) halogenoalkane, which can be the same or different configuration.

IUPAC and Common Nomenclature

Because an alkyl halide (or haloalkane) is formed by replacing just one hydrogen atom, the nomenclature scheme is similar to alkanes. The common names of alkyl halides are two parts: the alkyl group’s name and the stem of the halogen’s name, with the suffix -ide.

Format of Common Name: alkyl name + halide name

The IUPAC system employs the parent alkane’s name with a prefix denoting the halogen substituents, followed by a number indicating the location of the substituent. Fluoro-, chloro-, bromo-, and iodo- are the prefixes. Ethyl chloride is the colloquial name for CH3CH2Cl, while chloroethane is the IUPAC name. The three sections of the IUPAC term for simple haloalkanes are listed below.

IUPAC Name Format: locator + parent alkane + halo prefix

Common names are given to alkyl halides with simple alkyl groups. IUPAC names are normally given to those with more carbon atoms. 

Alkane Halogen Derivatives and Their Applications

Applications of alkane halogen derivatives 

• As a solvent, halogen-alkane derivatives such as carbon tetrachloride (CCl4), dichloromethane (CH2Cl2), and chloroform (CHCl3) are commonly used. They’re also used to clean oily substances, aerosols, and various machines.
• Refrigerators and air conditioners use liquefied halogen-alkanes as the refrigerant liquid. The most important are Freon-11 (CCl2F2) and Freon-12 (CClF2CClF2).

Freon-11 and Freon-12 have boiling points of 24°C and 30°C, respectively.

• CCl4, CBr2, CIF (commercial names are B, C, F), and other fire extinguishers.
• CHCl3, Fluthane, Halothane, and other anaesthetics.

Applications of aromatic halogen derivatives

• Used in D.D.T., alderin, deldrin, gammexane, and other pesticides.

• Have the capacity of a solvent.
• Used an intermediary in the manufacture of several substances.

Conclusion

Haloalkanes and haloarenes are organic compounds with one or more halogen atoms replacing one or more hydrogen atoms. Haloalkanes are compounds with a halogen group attached to an aliphatic chain, whereas haloarenes are compounds with a halogen group coupled to an aromatic ring.