Textbook Question
Draw a structure for each compound (includes old and new names).
a. 3-methylpent-1-ene
b. cis-3-methyl-3-hexene
c. 3,4-dibromobut-1-ene
4. Alkanes and Cycloalkanes
Naming Alkenes
6:57 minutesProblem 5d,e
Textbook Question
Give the systematic (IUPAC) names of the following alkenes.
(d) 
(e) 
Verified step by step guidance1
Identify the longest carbon chain that contains the maximum number of double bonds. In this case, the chain is five carbons long.
Number the carbon chain starting from the end nearest to the first double bond. This ensures the lowest possible numbers for the double bonds.
Identify the positions of the double bonds. Here, the double bonds are between carbons 1 and 2, 2 and 3, and 4 and 5.
Use the appropriate suffix for alkenes, which is '-ene'. Since there are multiple double bonds, use the suffix '-triene' to indicate three double bonds.
Combine the information to form the IUPAC name: Start with the numbers indicating the positions of the double bonds, followed by the name of the parent chain with the appropriate suffix.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
IUPAC Nomenclature
The International Union of Pure and Applied Chemistry (IUPAC) nomenclature is a standardized method for naming chemical compounds. It ensures that each compound has a unique and universally accepted name. For alkenes, the longest carbon chain containing the double bond is identified, and the chain is numbered to give the double bond the lowest possible number. Substituents are named and numbered accordingly.
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Alkene Structure
Alkenes are hydrocarbons that contain at least one carbon-carbon double bond (C=C). The presence of this double bond affects the geometry and reactivity of the molecule. In the given compound, CH2=C=CH-CH=CH2, there are multiple double bonds, which must be considered when determining the IUPAC name, as they influence the numbering and naming of the compound.
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Cumulative Double Bonds
Cumulative double bonds occur when two or more double bonds are directly adjacent to each other, as seen in the structure CH2=C=CH-CH=CH2. This arrangement is known as a cumulene. Cumulenes have unique properties and naming conventions in IUPAC nomenclature, where the position and number of double bonds are indicated in the name, and the longest chain containing the most double bonds is prioritized.
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