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Organic Chemical Nomenclature

There are two main classes of compounds (chemical), inorganic and organic. The compounds which were of mineral origin were known as inorganic and those of vegetable or animal origin were called organic chemicals. Organic chemicals are carbon containing chemicals.


 The term nomenclature means naming. The existence of large number of organic chemicals is responsible for evolving a definite systematic method for naming organic chemicals. There are two systems of naming organic chemicals. They are:Trivial system of nomenclatureIUPAC system of nomenclature 


 Trivial system of nomenclature:In the early days of organic chemistry, each new organic chemical was given an individual name. Such a name was based on the source, some property or some other trivial reason. Thus formic acid was so formed as it was obtained by distillation of red ants (Latin Formica="red" ants). An ordinary name given to the compound without reference to its structure is called a common name or Trivial name. 


The common names are like nicknames.IUPAC System of nomenclature:With the rapid growth of chemistry, the number of compounds increased fantastically. It became impossible to give common names to such a large number of compounds.In 1957, the International union of Pure and Applied chemistry evolved a scheme for giving systematic names to organic chemical on the basis of structure. This type of nomenclature is called IUPAC system of nomenclature. This system has set rules for naming organic molecules from their structures. 


 The systematic name of an organic chemical derived from its structural formula by applying IUPAC rules, is referred to as its IUPAC name. One organic chemical can have only one IUPAC name. It is superior to common name as it gives an insight in to the structure of the molecule. Knowing the IUPAC name of the compound, we can once write its structural formula. Common name identify the compounds while the IUPAC names represents the structure.IUPAC nomenclature is increasingly used in current practice. However common names of first few members of homologous series have been retained in the IUPAC system. 


The IUPAC name of a compound contains three parts namely rootword, suffix and prefix.Rootword: This indicates the number of carbon atoms in the longest chain. For example if it contains one carbon then the rootword is ‘meth’.Suffix: To the rootword suffix is added to indicate the functional group present in the molecule. For example, saturated hydrocarbon ‘ane’.Prefix: There are two types of prefixes. Primary prefix and secondary prefix. Primary prefix cyclo is used to differentiate a cyclic compound from a acyclic compound. A secondary prefix is added before rootword to designate the attached substituent groups.