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Question
Define a homologous series.
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Solution
A series of compounds with similar chemical properties, in which members differ from one another by an additional CH2 group, is called a homologous series.
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RELATED QUESTIONS
Classify the following carbon compounds into two homologous series and name them.
C3H4, C3H6, C4H6, C4H8, C5H8, C5H10
Write the name and formula of the 2nd member of homologous series having general formula CnH2n.
Write the molecular formula of first two members of homologous series having functional group -Cl.
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 |
| CnH2n−2 | (A) ______ | (B) ______ | (C) ______ |
| CnH2n+2 | (B) ______ | (E) ______ | (F) ______ |
Give the molecular formula of one homologue of the following:
C2H6
The molecular formula of a homologue of butane is ______.
Give the names and the structural formula of the first three members of the homologous series of alkanes.
Give the names of the first four members of the homologous series of
alkynes.
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?
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.
Assertion (A): In a homologous series of alcohols, the formula for the second member is C2H5OH and the third member is C3H7OH.
Reason (R): The difference between the molecular masses of the two consecutive members of a homologous series is 144.
The unsaturated hydrocarbons containing a carbon-carbon double bond are called _______.
While going in an increasing order of the length there is a rise in the molecular mass of the members by ______.
The general molecular formula for the homologous series of alkynes is _______.
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 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 following organic compound:
The first homologue whose general formula is CnH2n.
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’.
Name the following:
Group of organic compounds where the successive members follow a regular structural pattern, successive compounds differ by a 'CH2' group.
