For nomenclature of alkenes in the IUPAC system, the longest chain of ...
(i) F or nomenclature of alkenes in IUPAC system. The longest chain of carbon atoms containing the double bond is selected.
(ii) Numbering of the chain is done from the end which is nearer to the double bond.
(iii) The suffix ‘ene’ replaces ‘ane’ of alkanes.
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For nomenclature of alkenes in the IUPAC system, the longest chain of ...
Nomenclature of Alkenes in the IUPAC System
The IUPAC system is a set of rules used for naming organic compounds. When it comes to naming alkenes, there are specific guidelines to follow. Let's break down the process step by step:
1. Selecting the Longest Chain
- The first step is to identify the longest chain of carbon atoms that contains the double bond.
- This chain forms the backbone of the alkene molecule.
- The double bond takes priority over any other functional groups present in the compound.
2. Numbering the Chain
- Once the longest chain is identified, numbering of the carbon atoms is done.
- The numbering starts from the end of the chain that is closer to the double bond.
- This ensures that the double bond gets the lowest possible number.
3. Replacing the Suffix
- In alkanes, the suffix is "ane." However, in alkenes, the suffix changes to "ene" to indicate the presence of a double bond.
- For example, if the alkane is named "butane," the corresponding alkene would be named "butene."
4. Naming the Substituents
- If there are any substituents attached to the alkene chain, they are named using prefixes such as methyl, ethyl, etc.
- The position of the substituents is indicated by the number of the carbon atom to which they are attached.
5. Naming the Double Bond
- The double bond is indicated by its position in the chain.
- The lower number of the two carbon atoms involved in the double bond is mentioned before the name of the alkene.
- For example, if the double bond is between the second and third carbon atoms, it would be named as "2-butene."
First Member of the Alkene Series
- The first member of the alkene series is CH2, which replaces n by 1 in CnH2n.
- This compound is known as methene. However, it has a very short life and is highly reactive.
- The first stable member of the alkene series is C2H4, which is named as ethylene (common name) or ethene (IUPAC name).
Correct Answer
- The correct statement for the nomenclature of alkenes in the IUPAC system is option 'B.'
- Numbering of the chain is done from the end that is nearer to the double bond. This ensures that the double bond gets the lowest possible number, as per the IUPAC rules.
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