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Question
What is called homologous series? Give any three of its characteristics?
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Solution
A homologous series is a group or a class of organic compounds having the same general formula and similar chemical properties in which the successive members differ by a -CH2 group.
Characteristics of homologous series:
- Each member of the series differs from the proceeding or succeeding member by one methylene group (-CH2) and hence by a molecular mass of 14 amu.
- All members of a homologous series contain the same elements and functional group.
- They are represented by a general molecular formula. Eg: Alkanes, C2H2n+2.
- The members in each homologous series show a regular gradation in their physical properties with respect to their increase in molecular mass.
- The chemical properties of the members of a homologous series are similar.
- All the members can be prepared by a common method.
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RELATED QUESTIONS
Write the molecular formula of first two members of homologous series having functional group – OH
The molecular formula of a homologue of butane is ______.
Succeeding members of a homologous series differ by ______.
Distinguish between homologous organs and analogous organs. In which category would you place wings of a bird and wings of a bat? Justify your answer giving a suitable reason.
The general molecular formula for the homologous series of alkynes is _______.
Which of the following does not belong to the same homologous series?
Study and complete the following table:
| Homologous series | Alkane | Alkyne |
| General formula | CnH2n+2 | 1. ______ |
| IUPAC name | 2. ______ | Ethyne |
| Common name | Marsh gas | 3. ______ |
Consider the carbon compounds having following molecular formula:
(i) C3H6 (ii) C3H8 (iii) C4H6 (iv) C6H6 (v) C6H12
- State the number of double covalent bonds present in C3H6.
- Write the formula of first member of the homologous series to which the carbon compound C4H6 belongs.
- Which one of the above compounds forms a ring structure of carbon atoms?
- Identify, which of the above compounds, is a member of alkane series.
Consider the following molecular formulae of carbon compounds:
(i) CH3COOH (ii) CH3OH (iii) C2H6 (iv) C3H4 (v) C4H8
- Which one of these compounds belongs to homologous series of alcohols?
- Identify the compound having triple bond between carbon-carbon atoms.
- Write the molecular formula of the first member of the homologous series to which CH3COOH belongs.
- Write the general formula of the series to which the compound C4H8 belongs.
Name the following:
Group of organic compounds where the successive members follow a regular structural pattern, successive compounds differ by a 'CH2' group.
