Homologous Series
Each successive member of a homologous series differs by CH2. This note is the detail description about homologous series.
Summary
Each successive member of a homologous series differs by CH2. This note is the detail description about homologous series.
Things to Remember
- All the members of the same series can’t be represented by the same general formula.
- Each successive member of a homologous series differs by CH2.
- All members of the series can be prepared by general methods of preparation.
- All members can show a gradual change in their physical properties such as specific gravity, melting point etc.
- All members of the same series have the same functional group. For example: Alcohol (-OH) , ether (-O)
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Homologous Series
A homologous series is a group of organic compounds, which has the same functional group, but two successive members differ by CH2 group.
Characteristics of homologous series
- All the members of the same series can't be represented by the same general formula. For example, the series of alkanes can be represented by general formula CnH2n+2.
- Each successive member of a homologous series differs by CH2.
- All members of the series show similar chemical properties.
- All members of the series can be prepared by general methods of preparation.
- All members can show a gradual change in their physical properties such as specific gravity, melting point, etc.
- All members of the same series have the same functional group. For example, Alcohol (-OH) , ether (-O)
Alkyl group:
The hydrocarbon unit derived by the removal of one hydrogen atom from an alkane is called alkyl group or the alkyl radical. The name of an alkyl radical is written by replacing the ending "ane" of the alkane with "ayl".
- H
i.e. Alkane -> Alkyl radical
| S.No | Alkanes | Alkyl Radicals |
| 1. | CH4 (Methane) | CH3 (Methyl) |
| 2. | C2H6 (Ethane) | C2H5 (Ethyl) |
| 3. | C3H8 (propane) | C3H7 (propyl) |
| 4. | C4H10 (Butane) | C4H9 (butyl) |
Functional group:
It is defined as an atom or group of atoms (radical) which determines the chemical behavior of the organic compounds.
| S.No | Name of functional group | Symbol of functional group | Organic compounds |
| 1. | Hydroxyl | OH | Alcohol |
| 2. | Ether | O | Ether |
| 3. | Amino | NH2 | Amme |
| 4. | Carboxylic acid | COOH | Acid |
| 5. | Aldehyde (formyl) | CHO | Aldehyde |
| 6. | Keto | CO | Ketone |
When an alkyl group combines with a functional group, an organic compound is formed. Example:
-CH3+ -OH \(\longrightarrow\) CH3OH
Lesson
Hydrocarbon And Their Derivatives
Subject
Science
Grade
Grade 10
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