Wize High School Grade 12 Chemistry Textbook > Organic Chemistry (Part 1: Functional Groups and Naming)
Naming Alkenes and Alkynes
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Naming Alkenes and Alkynes
Wize Concept
1. The parent chain must include the alkene or alkyne (must contain a multiple bond)
2. When numbering the longest chain, number it so that the multiple bond gets the lowest possible number.
3. To indicate where the double bond is in the parent chain, we write the prefix for the long chain-(# of C atom that begins the multiple bond)-suffix (either ene or yne depending on if it is an alkene or alkyne). For example, if the molecule has 5 carbons in a straight chain, and a double bond is between carbons 2 and 3, we write: pent-2-ene.
Note: For cycloalkenes and cycloalkynes, naming is the same as for cycloalkanes but the double or triple bond is given the 1-2 position (since we want it to have the lowest numbers) and the other substituents are numbered to give the lowest combination of numbers.
Example: Name the following molecule
But-1-ene or butene would both be correct.
Example: Name the following molecule
hex-3-yne
Example: Name the following molecule
3,5-dimethylcyclohex-1-ene or 3,5-dimethylcyclohexene
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