Homologous series
A series of compounds of similar structure in which each member differs from the next by a common repeating unit, CH2 . The members of the series are called homologues.
A homologous series refers to a series of organic compounds that have the same general formula and similar chemical properties. Each member of the series differs from the previous member by a specific unit called a methylene (-CH2-) group.
For example, the homologous series of alkanes can be represented by the general formula CnH2n+2, where n is the number of carbon atoms in the molecule. The following table represents the first ten members of the series:
| Name | Molecular Formula |
|———-|——————|
| Methane | CH4 |
| Ethane | C2H6 |
| Propane | C3H8 |
| Butane | C4H10 |
| Pentane | C5H12 |
| Hexane | C6H14 |
| Heptane | C7H16 |
| Octane | C8H18 |
| Nonane | C9H20 |
| Decane | C10H22 |
As we can see, each member of the series differs from the previous one by a -CH2- group. This results in an increase in molecular weight, boiling point, and other physical properties.
The concept of homologous series is crucial in organic chemistry as it helps to predict the properties of the compounds that have not been synthesized yet. It also simplifies the classification of organic compounds and makes their study more systematic.
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