Notes On Organic Compounds: Nomenclature-General Rules - CBSE Class 11 Chemistry
The system of assigning a name to a compound is known as nomenclature. There are two systems for naming organic compounds
  • Common or trivial system 
  • IUPAC system

The trivial names are given on the basis of the source and certain properties of organic compounds.
Ex: Citric acid is named, as it is found in citrus fruits.

In the year 1947 the IUPAC that is the International Union of Pure and Applied Chemistry system of naming compounds was first developed.

The IUPAC system is a systematic nomenclature in which the name of a compound correlates to its molecular structure.

The IUPAC name of an organic compound consists of three parts the word root, the suffix and the prefix.
 

 
The word root indicates the number of Carbon atoms present in the selected longest chain.

Ex:
       Name of the
      Carbon Atoms
      Root Word
               C1     Meth
               C2     Eth
               C3      Prop
               C4      But
               C5      Pent
               C6      Hex
               C7      Hept
               C8      Oct
               C9      Non
               C10      Dec

A primary suffix is added to the end of the root word. It indicates whether a compound is saturated (or) unsaturated.

The three primary suffixes are, “ane” for alkane, “ene” for alkene and “yne” for alkyne.

A primary prefix is used to differentiate acyclic and cyclic compounds. But the rules for using these are slightly different.

Ex: In cyclic compounds, the prefix cyclo is added before the word root.



A secondary suffix indicates the nature of the functional group present in a compound.
   Organic Compound    Functional Group    Secondary Suffix
   Alcohols   -OH   -ol
   Aldehydes   -CHO   -al
   Ketones   >CO   -one
  Carboxylic acid   -COOH   -oic aid
  Acid amides   -CONH2   -amide
  Acid chlorides   -COCl   -oyl chloride
  Esters   -COOR   -alkyl...oate
  Cyanides   -CN   -nitrile
  Thioalcohols   -SH   -thiol
  Amines   -NH2   -amine


In the IUPAC system some groups are not considered as functional groups, they treated as substituent groups. In such cases, the substituent acts as the secondary prefix

Summary

The system of assigning a name to a compound is known as nomenclature. There are two systems for naming organic compounds
  • Common or trivial system 
  • IUPAC system

The trivial names are given on the basis of the source and certain properties of organic compounds.
Ex: Citric acid is named, as it is found in citrus fruits.

In the year 1947 the IUPAC that is the International Union of Pure and Applied Chemistry system of naming compounds was first developed.

The IUPAC system is a systematic nomenclature in which the name of a compound correlates to its molecular structure.

The IUPAC name of an organic compound consists of three parts the word root, the suffix and the prefix.
 

 
The word root indicates the number of Carbon atoms present in the selected longest chain.

Ex:
       Name of the
      Carbon Atoms
      Root Word
               C1     Meth
               C2     Eth
               C3      Prop
               C4      But
               C5      Pent
               C6      Hex
               C7      Hept
               C8      Oct
               C9      Non
               C10      Dec

A primary suffix is added to the end of the root word. It indicates whether a compound is saturated (or) unsaturated.

The three primary suffixes are, “ane” for alkane, “ene” for alkene and “yne” for alkyne.

A primary prefix is used to differentiate acyclic and cyclic compounds. But the rules for using these are slightly different.

Ex: In cyclic compounds, the prefix cyclo is added before the word root.



A secondary suffix indicates the nature of the functional group present in a compound.
   Organic Compound    Functional Group    Secondary Suffix
   Alcohols   -OH   -ol
   Aldehydes   -CHO   -al
   Ketones   >CO   -one
  Carboxylic acid   -COOH   -oic aid
  Acid amides   -CONH2   -amide
  Acid chlorides   -COCl   -oyl chloride
  Esters   -COOR   -alkyl...oate
  Cyanides   -CN   -nitrile
  Thioalcohols   -SH   -thiol
  Amines   -NH2   -amine


In the IUPAC system some groups are not considered as functional groups, they treated as substituent groups. In such cases, the substituent acts as the secondary prefix

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