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प्रश्न
What is called homologous series? Give any three of its characteristics?
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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
Classify the following carbon compounds into two homologous series and name them.
C3H4, C3H6, C4H6, C4H8, C5H8, C5H10
Give the structural formula for 1, 2-dichloroethane
Give the molecular formula of one homologue of the following:
C3H6
Give the names and the structural formula of the first three members of the homologous series of alkanes.
What is homologous series ?
Copy and complete the following table, which relates to the three homologous 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 |
The phenomenon in which compounds having different structural formulae have the same molecular formula is called _______.
Cyclohexane : Cyclic hydrocarbon : : Isobutylene : _______
Complete the following table for homologous series of Alkenes.
| Name | Molecular formula | Condensed structural formula | Number of carbon atom | Number of -CH2- units | Boiling point °C |
| Ethene | C2H4 | CH2 = CH2 | 2 | 0 | -102 |
| Propene | C3H6 | CH3–CH = CH2 | 3 | 1 | -48 |
| 1-Butene | C4H8 | CH3–CH2–CH = CH2 | ______ | ______ | -6.5 |
| 1-Pentene | C5H10 | CH3–CH2–CH2–CH = CH2 | ______ | ______ | 30 |
Name the third homologue of aldehydes.
