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Ch.12 Introduction to Organic Chemistry: Alkanes
McMurry - Fundamentals of GOB 8th Edition
McMurry8th EditionFundamentals of GOBISBN: 9780134015187Not the one you use?Change textbook
Chapter 12, Problem 20c

What is wrong with the following names? It will be helpful to draw the structures as named before making your decision.
c. 1-Ethyl-2-methyl-3-ethylcyclopentane

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1
Draw the structure of the compound as named: Start with a cyclopentane ring (a five-membered ring of carbon atoms). Add the substituents as specified in the name: an ethyl group at carbon 1, a methyl group at carbon 2, and another ethyl group at carbon 3.
Check for redundancy or incorrect naming: In IUPAC nomenclature, substituents should be listed in alphabetical order, and the numbering of the ring should minimize the locants (the numbers assigned to substituents).
Identify the issue: Having two ethyl groups on the ring (at carbons 1 and 3) violates the rule of using the simplest and most systematic name. Instead of naming them separately, they should be combined into a single substituent name if possible.
Reassign the numbering: To minimize the locants, renumber the ring so that the substituents are assigned the lowest possible numbers. For example, start numbering from the carbon with the first substituent alphabetically (ethyl) and proceed in a direction that minimizes the sum of the locants.
Provide the corrected name: After renumbering and combining substituents appropriately, rewrite the name of the compound following IUPAC rules. Ensure that the substituents are listed in alphabetical order and the numbering is correct.

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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 systematic method for naming chemical compounds. It provides rules for constructing names based on the structure of the molecule, ensuring that each name conveys specific information about the compound's structure, including the arrangement of atoms and functional groups.
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Cycloalkanes

Cycloalkanes are hydrocarbons that contain carbon atoms arranged in a ring structure. The naming of cycloalkanes follows specific conventions, where the prefix 'cyclo-' is used, and the position of substituents must be indicated clearly to avoid ambiguity in the compound's structure.
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Substituent Positioning

In organic chemistry, substituent positioning refers to the correct identification and numbering of substituents on a parent hydrocarbon chain or ring. Proper positioning is crucial to avoid confusion and ensure that the name accurately reflects the compound's structure, particularly in complex molecules with multiple substituents.
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Naming Alkanes with Substituents Example 1