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प्रश्न
Define homologous series of organic compounds. List its two characteristics. Write the name and formula of the first member of the series of alkenes.
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उत्तर
A homologous series is a series of carbon compounds that have different number of carbon atoms but contain the same functional group.
For example, methane, ethane, propane, butane, etc. are all part of the alkane homologous series.
Methane CH4
Ethane CH3CH3
Propane CH3CH2CH3
Butane CH3CH2CH2CH3
There is a difference of −CH2 unit between each successive compound.
Characteristics of homologous series:
All the members of the homologous series have same functional groups and hence similar chemical properties.
Two successive members of a homologous series differ by a −CH2 unit and 14u.
The first member of the series of alkenes in ethene. Its formula is C2H4.
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संबंधित प्रश्न
Write the molecular formula of first two members of homologous series having functional group – OH
Write the molecular formula of the third member of the homologous series of carbon compounds with general formula CnHO2n+1OH.
The number of carbon atoms present in the molecule of fifth member of the homologous series of alkynes is:
(a) four
(b) five
(c) six
(d) seven
.
Write names of first four homologous series of alcohols.
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?
Write a short note.
Homologous series
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 |
A carbon compound ‘A’ having melting point 156K and boiling point 351K, with molecular formula C2H6O is soluble in water in all proportions.
- Identify ‘A’ and draw its electron dot structure.
- Give the molecular formulae of any two homologues of ‘A’.
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?
