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प्रश्न
What is called homologous series? Give any three of its characteristics?
उत्तर
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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संबंधित प्रश्न
What is meant by homologous series of carbon compounds?
Write the name and formula of the 2nd member of homologous series having general formula CnH2n + 2.
Write the name and formula of the 2nd member of homologous series having general formula CnH2n – 2.
Complete the following table which relates to the homologous series of hydrocarbons.
|
General Formula |
IUPAC name of the homologous series | Characteristic bond type | IUPAC name of the first member of the series |
| `C_nH_(2n-2)` | (A)________ | (B)______ | (C)______ |
| C_nH_(2n+1) | (B)________ | (E)______ | (F)______ |
Copy and complete the following table which relates to three homologus series of hydrocarbons:
| General formula | CnH2n | CnH2n-2 | CnH2n+2 |
| IUPAC name of the homologus series | |||
| Characteristic bond type | Single bonds | ||
| IUPAC name of the first member of the series | |||
| Type of reaction with chlorine | Addition |
What is the difference in the molecular formula of any two adjacent homologues:
(i) In terms of molecular mass
(ii) In terms of number and kind of atoms per molecule?
Saturated hydrocarbon : Single bond : : Unsaturated hydrocarbon : _______
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) C2H2 (ii) C2H5 (iii) C3H7OH (iv) C2H6COOH (v) CH3CHO
- Identify which one of the above compounds, is a member of aldehyde series.
- Write the general formula of the series to which compound C2H2 belongs.
- Which one of the above compounds has triple bonds between carbon-carbon atoms?
- Write the molecular formula of the first member of the homologous series to which the compound C3H7OH belongs.
Name and draw the electron dot structure of first homologue of alkynes series.
