Textbook Question
What is each compound's systematic name?
a.
b.
4. Alkanes and Cycloalkanes
Naming Alkenes
5:32 minutesProblem 7c,d
Textbook Question
The following names are all incorrect. Draw the structure represented by the incorrect name (or a consistent structure if the name is ambiguous), and give your drawing the correct name.
c. 2-methylcyclopentene
d. 6-chlorocyclohexadiene
Verified step by step guidance1
Step 1: Understand the structure implied by the incorrect name '2-methylcyclopentene'. Cyclopentene is a five-membered ring with one double bond. The '2-methyl' suggests a methyl group attached to the second carbon of the ring.
Step 2: Draw the structure of cyclopentene. Start by sketching a five-membered ring and place a double bond between any two adjacent carbons.
Step 3: Add the methyl group to the second carbon of the cyclopentene ring. Number the carbons in the ring starting from the double bond to ensure the methyl group is correctly placed.
Step 4: Recognize that the name '2-methylcyclopentene' is incorrect because the double bond should be at the lowest possible number. The correct name should reflect the position of the double bond and the substituent.
Step 5: For '6-chlorocyclohexadiene', recognize that cyclohexadiene is a six-membered ring with two double bonds. The numbering should start from the position that gives the lowest numbers to the double bonds. Since '6-chloro' is not possible in a six-membered ring, redraw the structure with the chlorine at a valid position and provide the correct name based on the lowest numbering for the double bonds and substituents.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
IUPAC Nomenclature
IUPAC nomenclature is a standardized system for naming chemical compounds. It ensures that each compound has a unique name based on its structure, including the identification of the longest carbon chain, functional groups, and substituents. Understanding this system is crucial for correctly naming organic compounds and identifying errors in given names.
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Cycloalkenes
Cycloalkenes are cyclic hydrocarbons containing one or more carbon-carbon double bonds. The naming of cycloalkenes involves identifying the position of the double bond and any substituents. For example, '2-methylcyclopentene' suggests a methyl group on the second carbon of a five-membered ring with a double bond, but the numbering must start from the double bond for accuracy.
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Substituent Positioning
Substituent positioning refers to the correct numbering of carbon atoms in a molecule to indicate the location of attached groups. In cyclic compounds, numbering starts from the point of highest priority, such as a double bond or functional group, and proceeds to give the lowest possible numbers to substituents. This concept is essential for correcting names like '6-chlorocyclohexadiene,' where numbering should reflect the actual structure.
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