Halogen DERIVATIVES of Alkanes

The compounds formed by the replacement of one or more HYDROGEN atoms of alkanes by halogen atoms are called halogen derivatives of alkanes.
Examples: CH3Cl (methyl CHLORIDE), C2H5 Br (ethyl bromide)

 

 

Classification

 

Halogen derivatives


Monohalogen
derivatives contain
one halogen atom
per molecule, 
e.g. CH3Cl

Dihalogen 
derivatives contain
two halogen atoms
per molecule,
e.g. CH2Cl2

Trihalogen 
derivatives contain
THREE halogen atoms
per molecule, 
e.g. CHCl3

Tetrahalogen 
derivatives contain
four halogen atoms 
per molecule, 
e.g. CCl4

 

 

Monohalogen Derivatives


They are also called alkyl halides. Their general formulais CnH2n+1 X where X = Cl, Br or I. They are also represented as R - X, where R stands for an alkyl group.
Nomenclature according to:
Common system - alkyl halide
IUPAC system - haloalkane

 

 

Classification of Monohalogen Derivatives of Alkanes or Alkyl Halides


Alkyl halides are classified into the following three classes depending on the number of alkyl groups ATTACHED to the carbon atom bearing the halogen atom:

Primary Alkyl Halide: The alkyl halide in which the carbon atom bearing the halogen atom is attached to not more than one other carbon atom or alkyl group is called a primary alkyl halide. 
General Structure: R - CH2 - X
Examples: CH3 - CH2 - Cl, CH3 - CH2 - Br

Secondary Alkyl Halide: The alkyl halide in which the carbon atom bearing the halogen atom is attached to two other carbon atoms or alkyl groups is called a secondary alkyl halide. In such halides, the halogen bearing carbon atom is attached to only one hydrogen atom. 
Example: (CH3)2CH - Cl (isopropyl chloride)

Tertiary Alkyl Halide: The alkyl halide in which the carbon atom bearing the halogen atom is attached to three other carbon atoms or alkyl groups is called a tertiary alkyl halide. In such halides, the halogen bearing carbon atom is devoid of any hydrogen atom.

Example: (CH3)3 C - Cl (tertiary butyl chloride)