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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
Write the name and formula of the 2nd member of homologous series having general formula CnH2n + 2.
Write the molecular formula of the third member of the homologous series of carbon compounds with general formula CnHO2n+1OH.
Give the names and the structural formula of the first three members of the homologous series of alkanes.
Write the name and molecular formula of the first member of the homologous series of alkynes.
Write names of first four homologous series of alcohols.
Haloalkanes react with alkalies to produce alcohol. Give the equation for the preparation of the second member of the homologous series of alcohol. State under what condition the reaction occurs.
Saturated hydrocarbon : Single bond : : Unsaturated hydrocarbon : _______
Complete the following table for homologous series of alcohols.
| Name | Molecular formula | Condensed structural formula | Number of carbon atom | Number of -CH2- units | Boiling point °C |
| Methanol | CH4O | CH3-OH | 1 | 1 | 63 |
| Ethanol | C2H6O | CH3–CH2-OH | 2 | 2 | 78 |
| Propanol | C3H8O | CH3–CH2–CH2-OH | ______ | ______ | 97 |
| Butanol | C4H10O | CH3–CH2–CH2–CH2–OH | ______ | ______ | 118 |
Complete the following chart by using examples given in brackets.
(isobutylene, cyclohexane, propane, cyclohexene, cyclopentane, benzene, propyne, isobutane, propene)
| Straight chain hydrocarbons | Branched chain hydrocarbons | Cyclic hydrocarbons |
