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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 4

There are two branched-chain isomers with the formula C7H16, where the longest chain in the molecule is six carbons long. Draw them.

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1
Step 1: Understand the problem. The molecular formula C₇H₁₆ represents an alkane (a hydrocarbon with only single bonds). The problem asks for two branched-chain isomers where the longest continuous chain is six carbons long.
Step 2: Recall the concept of isomerism. Structural isomers have the same molecular formula but different connectivity of atoms. In this case, the isomers must have a six-carbon chain as the longest chain, with one carbon atom branching off.
Step 3: Draw the first isomer. Start with a six-carbon chain (hexane). Add a single carbon branch (methyl group) to the second carbon in the chain. This structure is called 2-methylhexane.
Step 4: Draw the second isomer. Again, start with a six-carbon chain. This time, add the single carbon branch (methyl group) to the third carbon in the chain. This structure is called 3-methylhexane.
Step 5: Verify the structures. Ensure that both isomers have the molecular formula C₇H₁₆, and confirm that the longest chain in each structure is six carbons long with one branch. These are the two branched-chain isomers requested.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Branched-Chain Isomers

Branched-chain isomers are compounds that have the same molecular formula but differ in the arrangement of their carbon skeletons. In the case of C₇H₁₆, these isomers can have different branching patterns, leading to distinct structural forms. Understanding how to visualize and draw these structures is essential for identifying the isomers.
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Isomers Concept 1

Structural Formula

The structural formula of a compound represents the arrangement of atoms within the molecule, including the connectivity between them. For branched-chain hydrocarbons, it is crucial to depict the longest continuous carbon chain and any branches accurately. This helps in distinguishing between different isomers and understanding their chemical properties.
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Longest Carbon Chain

The longest carbon chain in a hydrocarbon is the primary chain that contains the most carbon atoms, which is used as the basis for naming the compound. In the context of C₇H₁₆, identifying the longest chain (six carbons) is vital for drawing the isomers correctly. This concept is fundamental in organic chemistry for determining the structure and nomenclature of alkanes.
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