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Question
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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Solution
| 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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