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Question
What is called homologous series? Give any three of its characteristics?
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 the 2nd and 3rd member of the homologous series where the first member is ethyne.
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)______ |
Give the molecular formula of one homologue of each of the following:
C2H6
Propane and ethane are ______.
Give the abbreviated formula of the third member of the alcohol.
Define homologous series of organic compounds. List its two characteristics. Write the name and formula of the first member of the series of alkenes.
The general formula of Alkane is _________________
While going in an increasing order there is a rise in the molecular mass of the consecutive members of the homologous series by _______.
Write the chemical formula of two consecutive homologous of organic compounds having functional group - OH.
What happens to the (i) boiling point and (ii) solubility of organic compounds of a homologous series as the molecular mass increases?
Name the third homologue of aldehydes.
