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प्रश्न
Write a short note.
Homologous series
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उत्तर
- The series of carbon compounds formed by joining the same functional group in the place of a particular hydrogen atom on the carbon chains having sequentially increasing length is called homologous series.
- There are different homologous series in accordance with the functional group. For example, homologous series of alcohols, homologous series of carboxylic acids, homologous series of aldehydes, etc.
- All the members of the homologous series are homologues of each other and they can be represented by the same general molecular formula.
- Physical properties generally show a gradual change with the increase in molecular mass in the series whereas chemical properties of the members of the series show similarity because of the presence of the same functional group in them.
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संबंधित प्रश्न
Give the structural formula for 1, 2-dichloroethane
What is the next higher homologue of methanol (CH3OH)?
What is the difference between two consecutive homologues:
(i) in terms of molecular mass?
(ii) in terms of number and kind of atoms per molecule?
Give the molecular formula of one homologue of the following:
C2H6
Give the name and structural formula of one homologue of the following:
CH3OH
What is a homologous series? Explain with an example.
The number of carbon atoms present in the molecule of fifth member of the homologous series of alkynes is ______.
Write the name and molecular formula of the first member of the homologous series of alkynes.
Define homologous series of organic compounds. List its two characteristics. Write the name and formula of the first member of the series of alkenes.
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.
Find the odd one out and give its explanation.
There are different general molecular formula for all members of the homologous series.
Complete the following table for the homologous series of alkanes.
| Name | Molecular formula | Condensed structural formula | Number of carbon atom | Number of -CH2- units | Boiling point °C |
| Methane | CH4 | CH4 | 1 | 1 | -162 |
| Ethane | C2H6 | CH3–CH3 | 2 | 2 | -88.5 |
| Propane | C3H8 | CH3–CH2–CH3 | 3 | 3 | -42 |
| Butane | C4H10 | CH3–CH2–CH2–CH3 | ______ | ______ | 0 |
| Pentane | C5H12 | CH3–CH2–CH2–CH2–CH3 | ______ | ______ | 36 |
| Hexane | C6H14 | CH3–CH2–CH2–CH2–CH2–CH3 | ______ | ______ | 69 |
Observe the structural formula and answer the following questions.
- Write the name of the given hydrocarbon.
- The given hydrocarbon is included in which type of hydrocarbon?
- What is the kind of compounds with the above characteristic structure called?
What is called homologous series? Give any three of its characteristics?
Name the following organic compound:
The first homologue whose general formula is CnH2n.
Study and complete the following table:
| Homologous series | Alkane | Alkyne |
| General formula | CnH2n+2 | 1. ______ |
| IUPAC name | 2. ______ | Ethyne |
| Common name | Marsh gas | 3. ______ |
Consider the carbon compounds having following molecular formula:
(i) C3H6 (ii) C3H8 (iii) C4H6 (iv) C6H6 (v) C6H12
- State the number of double covalent bonds present in C3H6.
- Write the formula of first member of the homologous series to which the carbon compound C4H6 belongs.
- Which one of the above compounds forms a ring structure of carbon atoms?
- Identify, which of the above compounds, is a member of alkane series.
Name the third homologue of aldehydes.
