Classification and Nomenclature Preparation and Properties

Classification and Nomenclature Preparation and Properties

→ Halogen derivatives are classified on diffrent basis — in IUPAC system of nomenclature, they are considered as halosubstituted derivatives of the respective alkanes.

→ The number of carbon atoms are used to consider the position of halogen atom, to which it is attached. The carbon atom carrying the halogen atom gets the lowest number. While writing the name, halogen is written as prefix.

Classification and Nomenclature Preparation and Properties

→ If two different halogen atoms are present in halogen derivatives then preference is given in both i.e., numbering and writing name, to that halogen atom which comes first in the alphabetical order. For example, 2-Bromo-3-Chlorobutane

Classification and Nomenclature Preparation and Properties 1

→ These may be classified as mono, di, tri, tetra etc. compounds depending on the number of halogen atoms present in haloalkanes. For example,

Monohalo Compounds

Classification and Nomenclature Preparation and Properties 2

Dihalo Compounds

Classification and Nomenclature Preparation and Properties 3

Trihalo Compounds

Classification and Nomenclature Preparation and Properties 4

Mono haloalkanes are classified into three types on the basis of nature of carbon to which halogen is attached.

Primary Alkyl Halides : In these compounds, halogen atom is attached with primary carbon atom. For example,

Classification and Nomenclature Preparation and Properties 5

Common Name : Methyl chloride, Ethyl chloride Propyl chloride.
IUPAC Name : Chioromethane, Chioroethane 1- Chloropropane.
Secondary Alkyl Halides : In these compounds, halogen atom is attached with secondary carbon atom.
For example,

Classification and Nomenclature Preparation and Properties 6

Tertiary Alkyl Halides : In these compounds, halogen atom is attached with tertiary carbon atom.
For example,

Classification and Nomenclature Preparation and Properties 7

→ Allylic Halides: In these compounds, the halogen atom is bonded to a sp3 -hybridised carbon atom next to carbon-carbon double bond. This sp3 hybridised carbon is known as allylic carbon. For example:

Classification and Nomenclature Preparation and Properties 8

→ Benzylic Halides : In these compounds, the halogen atom is bonded to a sp3 -hybridised carbon atom next to an aromatic ring. This carbon is known as benzylic carbon.

Classification and Nomenclature Preparation and Properties 9

→ Vinylic Halides : In these compounds, the halogen atom is bonded to a sp2 -hybridised carbon atom of a carbon-carbon double bond.

Classification and Nomenclature Preparation and Properties 10

→ Aryl Halides or Haloarenes : In these compounds, halogen atom is bonded to the sp2-hybridised carbon atom of an aromatic ring. These are represented as Ar-X. For example,

Classification and Nomenclature Preparation and Properties 11

Chemistry Notes