Nomenclature of Organic Compounds: chemistry
Need of IUPAC Nomenclature
Initially there was not a certain fashion to decide the names of organic compounds. The names were decided in many ways.
Some organic compound got their name on the basis of areas where they were discovered first, some were named after the scientists, some were named according to color, while some were named after near and dear of the scientists who discovered them.
Example
(1) Formic Acid
Formic acid is naturally occurring in the body of red ants, wood ants, mound ants, thatching ants, etc.
And hence, the formic acid got its name after a Greek word "formica". Formica is a genus of ant's family Formicidae.
(2) Lactic Acid
Lactic acid naturally occurs in milk. And it got its name after a Latin word "Lac" which means "milk".
(3) Ethane
The name of Ethane comes from the Greek word "Aithen" which means "kindle or blaze" because ethane is an inflammable gas.
(4) Barbituric acid
This barbituric acid was discovered by a German scientist Adolf von Baeyer. He named it after one of his lady friends "Barbara". Another story tells that the scientist Adolf von Baeyer named this compound after "Saint Barbara".
This appeared well initially, but with discoveries of more and more organic compounds, a systematic method of naming was started needed.
Examples of some organic compound with common name
Structural Formula of Hexane and its name
The organic compound having molecular formula C6H14 is called the Hexane
(a) The structural formula of Hexane is given below:
CH3. CH2.CH2.CH2. CH2. CH3.
Or,
The structural formula of Hexane
This is called n–hexane.
(b) When one carbon atom is attached with the second carbon atom, the structural formula becomes.
The common name of this structure is Iso-hexane
(c) But, when the carbon atom from the second position is attached to the third position of carbon in the straight chain, there is confusion in the naming. In this condition, there is no common name for this organic molecule.
There is no common name for this structure.
(d) If two carbon atoms get attached with the second carbon atom, this organic compound becomes Neo-hexane
The common name or trivial name of this organic compound is Neo-hexane
(e) But when one of the carbon atoms gets attached to the third carbon atom, the structure of the given organic compound becomes as follows:
The structure of this organic compound has no common name.
(b) Let us take another example of Pentyl Chloride
The molecular formula of pentyl chloride is C5H11.
Now, when the chloride group is attached to the second carbon atom, the structure becomes
The common name of this organic compound is also pentyl chloride, but there is difference between structural formula.
The common name of this organic compound is also pentyl chloride, but structural formula is different.
In this way we can see that instead of having different types of structures, many compounds have the same common names, which creates so many problems. Using common names it becomes difficult to differentiate among many organic compounds.
Thus, to overcome these problems a systematic naming system was needed.
IUPAC Naming System
An international body International Union of Pure and Applied Chemistry, popularly known as "IUPAC" or "you-pack", recommended a naming system. This naming system, IUPAC Nomenclature adopted unanimously in the meet held in 1957 in Paris.
A book, Nomenclature of Organic Compounds, was published after that, this book is informally called as "Blue Book" also.
This IUPAC system of nomenclature provides a set of rules to name the organic compounds.
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