Try to draw different structures for the following carbon compounds and name the isomers of each (Take the help of your teacher)
(a)C5H12 (b)C6H14
Homologous series
Till now we have classified Organic compounds on the basis of carbon chains and functional groups. There is another classification based on Homologous series
The series of carbon compounds in which two successive compounds differ by-CH2 unit is called homologous series.
Eg:1)CH4' C2H6' C3H8........
2)CH3 OH, C2H5 OH,C3H?OH.......
If you observe above series of compounds, you will notice that each compound in the series differs by-CH, unit by its successive compound Homologous series of organic compounds have following
characteristic features
1) They have one general formula.
Eg: alkanes (CnH2n+2);alkynes(CnH2n-2)OH etc.
2) Successive compounds in the series possess a difference of (-CH 2)
unit.
3) They possess similar chemical properties due to the same functional group
Eg: alcohols, aldehydes and carboxylic acids have functional groups C-OH, C-CHO and C-COOH respectively
4) They show a regular gradation in their physical properties (see the table-1).
For example: we may take alkanes, alkenes, alkynes, alcohols, aldehydes, and carboxylic acids etc. as homologous series. The individual members of a homologous series are called homologs.
Observe the following tables 1, 2 and 3, They represent three different
homologous series.
Table-1: Homologous series of Alkanes
The general formula of this homologous series Alkanes is CnH2n+2,where n=1,2,3.....
