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प्रश्न
Study and complete the following table:
| Homologous series | Alkane | Alkyne |
| General formula | CnH2n+2 | 1. ______ |
| IUPAC name | 2. ______ | Ethyne |
| Common name | Marsh gas | 3. ______ |
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उत्तर
| Homologous series | Alkane | Alkyne |
| General formula | CnH2n+2 | 1. CnH2n−2 |
| IUPAC name | 2. Methane | Ethyne |
| Common name | Marsh gas | 3. Acetylene |
Explanation:
1. The general formula of the alkyne is CnH2n−2· Due to the presence of triple bond four hydrogens are removed from the molecular formula of alkane. For example, in the case of ethyne, the two carbons have already formed triple bonds therefore they only need one more bond in order to complete their octet.
2. The IUPAC name of the first member of the alkane family is methane. Also, the common name given in the table is Marsh gas which is the common name of methane gas.
3. The common name of ethyne is acetylene as it contains the acetyl group. This name was coined by a French chemist (Marcelin-Pierre-Eugene Berthelot) in 1864.
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संबंधित प्रश्न
Write the name and formula of the 2nd member of homologous series having general formula CnH2n.
Write the molecular formula of the 2nd and 3rd member of the homologous series where the first member is ethyne.
What is the difference between two consecutive homologues:
(1) in terms of molecular mass?
(2) in terms of number and kind of atoms per molecule?
What is a homologous series? Explain with an example.
The molecular formula of an organic compound is C18H36. Name its homologous series.
Give the names of the first four members of the homologous series of
alkynes.
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 |
Consider the carbon compounds having following molecular formula:
(i) C2H2 (ii) C2H5 (iii) C3H7OH (iv) C2H6COOH (v) CH3CHO
- Identify which one of the above compounds, is a member of aldehyde series.
- Write the general formula of the series to which compound C2H2 belongs.
- Which one of the above compounds has triple bonds between carbon-carbon atoms?
- Write the molecular formula of the first member of the homologous series to which the compound C3H7OH belongs.
