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how to find out the number of isomers for a given hydrocarbon.
    Isomers are compounds which have the same molecular formula but a different structural formula.

Structural Formula:
           The structural formula (also called the displayed formula) shows how the atoms are joined together in the molecule.
         Isomers of hydrocarbons have the same number of carbon and hydrogen atoms but the carbon atoms are joined to each other in different ways.

Isomers of Butane

Butane (C4H10) has two structural isomers.
Isomer 1 is the straight chain normal structure for butane
(called n-butane).



                 n Butane

Isomer 2 (called 2-methylpropane) is a different structure
with a branched chain which has a carbon* atom
joined onto three other carbon atoms.


           2 methyl Propane

The two isomers are different compounds with different boiling points.

Isomers of pentane

i) n Pentane


ii) 2 Methyl Butane
iii) 2,2 dimethyl propane

Changing the shape of the molecule does not produce
a different isomer. A different isomer can only be made by changing the way in which the carbon atoms are joined together.

The more carbon atoms a compound has,the greater the number of isomers there can be.

 Hydrocarbon      no.of Carbons      no. of Isomers
  1. Propane                 3                        0
  2. Butane                   4                        2
  3. Pentane                  5                        3
  4. Hexane                   6                        5  
  5. Heptane                  7                        9
  6. Octane                    8                      15
There are also isomers of alkenes and alcohols.


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