Question

Draw structures of the nine isomers of \(\mathrm{C}_{7} \mathrm{H}_{16}\)

Short answer

The nine isomers are heptane, 2-methylhexane, 3-methylhexane, 2,2-dimethylpentane, 2,3-dimethylpentane, 3-ethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane, and 2,2,3-trimethylbutane.

Step-by-step solution

Understand the concept of isomers

Isomers are compounds with the same molecular formula but with different arrangements of atoms. For \( ext{C}_7 ext{H}_{16}\), we need to explore different structural arrangements.

Identify possible carbon chain lengths

Start with the longest continuous carbon chain: heptane with 7 carbon atoms. Continue with shorter chains, considering all possible branching points.

Draw straight-chain isomers

The straight chain is solely heptane: \[\text{CH}_3(\text{CH}_2)_5\text{CH}_3\]

Draw branched isomers with a 6-carbon chain

With a 6-carbon chain (hexane), add one methyl group:1. 2-Methylhexane: \[\text{CH}_3-\text{CH}-(\text{CH}_3)-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_3\]2. 3-Methylhexane: \[\text{CH}_3-\text{CH}_2-(\text{CH}_3)-\text{CH}_2-\text{CH}_2-\text{CH}_3\]3. 2,2-Dimethylpentane:\[\text{CH}_3-\text{CH}-(\text{CH}_3)_2-\text{CH}_2-\text{CH}_3\]4. 2,3-Dimethylpentane:\[\text{CH}_3-\text{CH}_2-(\text{CH}_3)-\text{CH}-(\text{CH}_3)-\text{CH}_3\]

Draw branched isomers with a 5-carbon chain

With a 5-carbon chain (pentane), add two methyl groups. 1. 3-Ethylpentane:\[\text{CH}_3-\text{CH}_2-(\text{C}_2\text{H}_5)-\text{CH}_2-\text{CH}_3\]2. 2,3-Dimethylpentane: previously drawn, included again for completeness.3. 2,4-Dimethylpentane:\[\text{CH}_3-\text{CH}_-(\text{CH}_3)-\text{CH}_2-(\text{CH}_3)-\text{CH}_3\]4. 3,3-Dimethylpentane:\[\text{CH}_3-\text{C}-(\text{CH}_3)_2-\text{CH}_2-\text{CH}_3\]

Verify the structures

Double-check that the structures conform to the molecular formula \(\text{C}_7\text{H}_{16}\) and that they are not duplicates. Ensure each represents a distinct isomer.

List all nine isomers

Compile all nine isomers: 1. Heptane 2. 2-Methylhexane 3. 3-Methylhexane 4. 2,2-Dimethylpentane 5. 2,3-Dimethylpentane 6. 3-Ethylpentane 7. 2,4-Dimethylpentane 8. 3,3-Dimethylpentane 9. 2,2,3-Trimethylbutane

Key concepts

Structural Isomers

In chemistry, structural isomers are fascinating compounds. They have the same molecular formula but differ in the arrangement of their atoms. This means they often have different properties, despite being made of the same elements. The beauty of structural isomers lies in their variety and the unique ways atoms can be arranged. Here’s what you need to know:

• They share the same total count of each type of atom.
• The differences in their arrangement give them different physical and chemical properties.

They offer insight into how structure affects function in molecules, making them a fundamental topic in organic chemistry.

C7H16 Isomers

The molecular formula \( \text{C}_7\text{H}_{16} \) represents heptane and its isomers, which are all alkanes. With seven carbon atoms, there are nine distinct structural isomers. Exploring these isomers helps you understand how the same atoms can create different structures. Here is a look at what these isomers entail:

• Straight-chain isomer: Heptane, with a linear chain of seven carbon atoms.
• Branched isomers: Created by reorganizing the carbon atoms to form various branches, resulting in isomers like 2-Methylhexane or 3-Ethylpentane.

These isomers reveal how molecular structure can be altered while maintaining the same molecular formula, offering a deeper comprehension of chemical diversity.

Branched Isomers

Branched isomers are an intriguing category where carbon chains are not in a straight line. Instead, they have branches, which can significantly affect the molecule's properties. Let’s dive into the details:

• Structure: A main carbon chain with one or more branches of carbon atoms.
• Example: 2,2-Dimethylpentane is a branched isomer where two methyl groups are attached to the second carbon atom.
• Properties: The branching often leads to lower boiling points compared to their straight-chain counterparts.

Understanding branched isomers is essential to grasp the complex nature of hydrocarbons and their interactions.