Nomenclature of Halogen Derivatives of Alkanes

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Isomerism in Haloalkanes: 

  • Isomers are the organic compounds, which have the same molecular formula but different structural formula and properties. The phenomenon is called isomerism. Haloalkanes can exhibit the following type of isomerism.

Chain Isomerism:

  • The haloalkanes with four or more carbon atoms exhibit this type of isomerism. This isomerism is exhibited due to the difference in the carbon chains.

Position Isomerism:

  • The haloalkanes with three or more carbon atoms exhibit this type of isomerism. This isomerism is exhibited due to the difference in the position of halogen group.

Optical Isomerism:

  • The haloalkanes which have the same molecular and structural formula, but have a different arrangement of the atoms or group of atoms in space and have a tendency to rotate the plane of polarised light are called optical isomers and the phenomenon is called optical isomerism.

Isomers of monochloro derivatives of 2,3-Dimethylbutane:

Structure of 2,3-Dimethylbutane is



The isomers of monochloro derivatives of 2,3-Dimethylbutane are

Isomers of C5H11Br and their classification:



  • Note: 2 – Bromo-2-methylbutane, 2 – Bromo-3-methylbutane, 1 – Bromo-3-methylbutane are enantiomers. i.e. they are optically active compounds

Isomers of C4H9Br and their classification: isomerism

Classification as a primary, secondary or tertiary alkyl halide.

1-Bromopropane 

  • Bromine atom is attached to a primary carbon i.e. this carbon is attached to only one carbon atom. Hence it is primary alkyl halide.

2-Bromopropane 

  • Bromine atom is attached to a secondary carbon i.e. this carbon is attached to two other carbon atoms. Hence it is secondary alkyl halide.

2-Bromo-2-methylpropane

  • Bromine atom is attached to a tertiary carbon i.e. this carbon is attached to three other carbon atoms. Hence it is tertiary alkyl halide.

Nomenclature:

Trivial or Common System of Nomenclature:

  • In the trivial system, haloalkanes are named as alkyl halides. The name is derived by adding the word halide to the name of the corresponding alkyl group. The trivial name is always written as two separate words.
  • e.g. CH3Br (Methyl bromide), CH3CH2Br (Ethyl bromide), CH3CH2Cl (Ethyl chloride).

Different Alkyl Groups With Examples:

Sr. Alkyl Group Name of Group Example Compound Name

1



CH3

Methyl CH3Cl Methyl chloride

2

CH3CH2–  or C2H5 Ethyl C2H5Br Ethyl bromide

3

CH3CH2CH2 n-Propyl CH3CH2CH2I n-Propyl iodide

4

iso-Propyl CH3CHBrCH3 iso-Propyl bromide

5



CH3CH2CH2CH2 n-Butyl CH3CH2CH2CH2I n-Butyl iodide
6 sec-Butyl CH3CHClCH2CH3 sec-Butyl iodide
7 iso-Butyl iso-Butyl chloride
8 tert-Butyl tert-Butyl bromide
9 neo-Pentyl neo-Pentylbromide

IUPAC Nomenclature:

No. Formula Common Name IUPAC Name
1 CH3Br methyl bromide Bromomethane
2 CH3CH2Br ethyl bromide Bromoethane
3 CH3CH2CH2Cl n-propyl chloride 1-Chloropropane
4 CH3CHClCH3 isopropyl chloride 2-Chloropropane
5 CH3CH2CH2CH2Cl n-butyl chloride 1-Chlorobutane
6 CH3CHClCH2CH3 sec-butyl chloride 2-Chlorobutane
7 (CH3)2CHCH2I isobutyl iodide 1-Iodo-2-methylpropane
8 (CH3)3CBr tert-butyl bromide 2-Bromo-2-methylpropane
9 (CH3)3CCH2Br neo-pentyl bromide 1-Bromo-2,2-dimethylpropane
10 CH2=CHCl vinyl chloride Chloroethene
11 CH2=CHCH2Cl allyl chloride 3-Chloroprop-1-ene

 To Draw Structure From IUPAC Name:

No. IUPAC Name

Structure

1

2-Iodo-3-methylpentane
2 3-Chlorohexane

3

1-Chloro-2,2-dimethylpropane
4 3-Bromo-2-methylpentane

5

2-Bromo-3-ethyl-2-methylhexane
6 1-Chlorobutane

CH3-CH2-CH2-CH2Cl



7

2-Bromo-2-methylpentane

8 1-chloro-2,2-dimethylpropane

 

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