Alkanes nomenclature

                  ALKANES   NOMENCLATURE

Alkanes has two types of names, common names and IUPAC names 

Common names

          In the past organic compounds were named on different bases:

On the method of preparation

          Acetic acid is prepared from vinegar (Latin acetum meaning vinegar).

On the name of the person who works on that compound

          A compound barbituric acid is made by a scientist Barbara.

On the base of the source from which that compound is prepared.

          The name of methane is marsh gas because; this gas is obtained from marshy places.

n, iso, and neo prefixes are used before the name of alkane. This method of nomenclature creates much confusion among the different peoples living in different parts of the world.

IUPAC Names 

          The international chemical congress sought out the problem of nomenclature of organic compounds in 1889. The international union of chemistry (IUC) gave a report of rules for nomenclature. This report is further modified by IUPAC (International union of pure and applied chemistry) in 1947. After that these rules are accepted and followed all over the world for the nomenclature of organic compounds. According to IUPAC, every compound has its own specific name.

Alkyl group

          When we remove one hydrogen from an alkane, then it is converted into an alkyl group. The “–ane ” of the corresponding alkane is converted into “–yl ” after the removal of one hydrogen atom.

     Alkane        -H          Alkyl

Methane          -H          Methyl

Nomenclature of alkanes

          There are many rules for the nomenclature of alkanes which are as follow:

1.          Always select the longest chain of carbon atoms in the whole molecule, which is designated as parent name of that compound.

• 2      Always try to number the carbon atom chain from that side where substituents get the lowest possible number.

3.     Always mention the position of substituents by the number on the carbon atom chain. Parent name is always placed at last which is followed by substituents name.

4.     If two or more substituents are present on the chain then each substituent is represented by its own number on the carbon atom chain. The representation of substituents follows the alphabetical rule.

5.     If different substituents present on the same carbon atom then we use that number in twice in the naming of that compound.

6.     If the same substituent is present more than one time on the carbon atom chain than we use prefixes di, tri, tetra, and so on. We also represent each substituent by its own number. The numbers in a name are separated by a comma. Substituents name and their position number is separated by dash (-).

7.     If we have two same chain lengths in the whole molecule then we choose that chain which have a greater number of substituents.