Question

Draw structural formulas for all isomeric alkanes having the general formula \(\mathrm{C}_{7} \mathrm{H}_{16}\).

Short answer

There are seven possible isomeric structures for alkanes with the formula C7H16: 1. Heptane (Linear Structure): \( \text{CH}_3-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_3 \) 2. 2-Methylhexane: \( \text{CH}_3-\text{CH}( \text{CH}_3 )-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_3 \) 3. 3-Methylhexane: \( \text{CH}_3-\text{CH}_2-\text{CH}( \text{CH}_3 )-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_3 \) 4. 2,2-Dimethylpentane: \( \text{CH}_3-\text{C}( \text{CH}_3 )_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_3 \) 5. 2,3-Dimethylpentane: \( \text{CH}_3-\text{CH}( \text{CH}_3 )-\text{CH}( \text{CH}_3 )-\text{CH}_2-\text{CH}_2-\text{CH}_3 \) 6. 2,4-Dimethylpentane: \( \text{CH}_3-\text{CH}( \text{CH}_3 )-\text{CH}_2-\text{CH}( \text{CH}_3 )-\text{CH}_2-\text{CH}_3 \) 7. 3,3-Dimethylpentane: \( \text{CH}_3-\text{CH}_2-\text{C}( \text{CH}_3 )_2-\text{CH}_2-\text{CH}_2-\text{CH}_3 \)

Step-by-step solution

Identify the Longest Carbon Chain

As we are dealing with alkanes, we first need to identify the longest continuous chain of carbon atoms in the molecule. For C7H16, the most extended carbon chain will have seven carbon atoms. There is only one way to arrange seven carbon atoms in a straight chain, and that is in a linear shape.

Identify the Branched Isomers

Next, we need to consider the possible branched isomers. These are the different ways carbon atoms can be connected to create structures that are not simply a straight chain. To do this, we can start by removing a carbon atom from the longest carbon chain and attaching it to the remaining chain in various ways as a side chain or branch.

Draw all Possible Isomeric Structures

We will now draw the structural formulas for the different isomers. The possible C7H16 isomers are: 1. Heptane (Linear Structure): This structure has a straight chain of 7 carbon atoms with no branches. \[ \text{CH}_3-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_3 \] 2. 2-Methylhexane: In this structure, we have a side chain with 1 carbon atom attached to the 2nd carbon atom from the end of a 6-carbon straight chain. \[ \text{CH}_3-\text{CH}( \text{CH}_3 )-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_3 \] 3. 3-Methylhexane: Similar to 2-Methylhexane, but the branch is attached to the 3rd carbon atom instead. \[ \text{CH}_3-\text{CH}_2-\text{CH}( \text{CH}_3 )-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_3 \] 4. 2,2-Dimethylpentane: In this structure, the 5-carbon straight chain has two 1-carbon branches, both attached to the 2nd carbon atom. \[ \text{CH}_3-\text{C}( \text{CH}_3 )_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_3 \] 5. 2,3-Dimethylpentane: Similar to 2,2-Dimethylpentane, but one branch is attached to the 2nd carbon atom while the other is attached to the 3rd carbon atom. \[ \text{CH}_3-\text{CH}( \text{CH}_3 )-\text{CH}( \text{CH}_3 )-\text{CH}_2-\text{CH}_2-\text{CH}_3 \] 6. 2,4-Dimethylpentane: Like the previous examples, but one branch is attached to the 2nd carbon atom while the other is attached to the 4th carbon atom. \[ \text{CH}_3-\text{CH}( \text{CH}_3 )-\text{CH}_2-\text{CH}( \text{CH}_3 )-\text{CH}_2-\text{CH}_3 \] 7. 3,3-Dimethylpentane: Just like 2,2-Dimethylpentane, but this time both branches are attached to the 3rd carbon atom. \[ \text{CH}_3-\text{CH}_2-\text{C}( \text{CH}_3 )_2-\text{CH}_2-\text{CH}_2-\text{CH}_3 \] These are the seven possible isomeric structures for alkanes with the formula C7H16.

Key concepts

Structural Isomers

Structural isomers are fascinating in the realm of organic chemistry. They represent molecules that have the same molecular formula but are arranged differently in space. This simple concept can lead to molecules with distinct properties and behaviors. For example, in alkanes with the formula \( \text{C}_7\text{H}_{16} \), structural isomers vary in their carbon atom arrangement.
Chemical properties significantly remain the same, but physical properties like boiling points or densities can differ markedly. Understanding structural isomers helps in synthetic chemistry, where specific arrangement leads to desired reaction outcomes.

• Isomers have the same number and types of atoms.
• Differences lie in branching or connectivity of atoms.
• Studying isomers helps to understand natural product synthesis and petrochemical processes.

Organic Chemistry

Organic chemistry, often called the chemistry of life, focuses on carbon-containing compounds. Its vastness encompasses billions of known compounds, with alkanes being fundamental structures.
Alkanes are hydrocarbons—compounds consisting solely of hydrogen and carbon—that serve as a foundation for more complex molecules. These compounds are saturated, meaning all carbon-carbon bonds are single bonds. Understanding the intricacies of organic molecules, like those of isomeric alkanes, allows chemists to grasp foundational principles and applications in other fields, including biochemistry and pharmacology.

• Central to many industrial applications.
• Key component in understanding biological transformations.
• Forms a basis for complex organic reactions.

Chemical Structure Drawing

Chemical structure drawing is a vital skill in chemistry, enabling scientists to visualize molecules. It represents molecular geometry, showing how atoms connect. For isomeric alkanes like \( \text{C}_7\text{H}_{16} \), this involves depicting different possible arrangements.
Drawing techniques range from simple line structures to more detailed three-dimensional models, depending on the information needed.
Well-drawn structures make it easier to predict the properties and reactivity of the compounds.

• Helps in predicting molecule behavior and interaction.
• Essential for communicating molecular information in research.
• Various representations exist, including line-angle and 3D models.