Question

Write structural formulas for the following alkanes. (a) \(2,2,4\) -trimethylpentane (b) 2,2 -dimethylpropane (c) 4-isopropyloctane (d) \(2,3,4\) -trimethylheptane

Short answer

Question: Draw the structural formula for the following alkanes: (a) 2,2,4-trimethylpentane, (b) 2,2-dimethylpropane, (c) 4-isopropyloctane, and (d) 2,3,4-trimethylheptane. Answer: (a) 2,2,4-trimethylpentane: \( \text{CH}_3-\text{C}(\text{CH}_3)_2-\text{CH}_2-\text{C}(\text{CH}_3)-\text{CH}_3\) (b) 2,2-dimethylpropane: \( \text{CH}_3-\text{C}(\text{CH}_3)_2-\text{CH}_3\) (c) 4-isopropyloctane: \( \text{CH}_3-\text{CH}_2-\text{CH}_2-\mathrm{C}(\mathrm{CH}_3)_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_3\) (d) 2,3,4-trimethylheptane: \( \text{CH}_3-\text{C}(\text{CH}_3)-\text{C}(\text{CH}_3)-\text{C}(\text{CH}_3)-\text{CH}_2-\text{CH}_2-\text{CH}_3\)

Step-by-step solution

(a) 2,2,4-trimethylpentane

1. Identify the main chain: 'Pentane' indicates a 5-carbon main chain. 2. Identify branching groups: 'Trimethyl' indicates 3 methyl (\(\text{CH}_3\)) groups are branched off the main chain. 3. Assign positions: The numbers 2, 2, and 4 indicate the positions of the methyl groups on the main chain. 4. Draw the full structural formula: \( \text{CH}_3-\text{C}(\text{CH}_3)_2-\text{CH}_2-\text{C}(\text{CH}_3)-\text{CH}_3\)

(b) 2,2-dimethylpropane

1. Identify the main chain: 'Propane' indicates a 3-carbon main chain. 2. Identify branching groups: 'Dimethyl' indicates 2 methyl (\(\text{CH}_3\)) groups are branched off the main chain. 3. Assign positions: The numbers 2 and 2 indicate the positions of the two methyl groups on the main chain. 4. Draw the full structural formula: \( \text{CH}_3-\text{C}(\text{CH}_3)_2-\text{CH}_3\)

(c) 4-Isopropyloctane

1. Identify the main chain: 'Octane' indicates an 8-carbon main chain. 2. Identify branching groups: 'Isopropyl' is an alkyl group with the formula \(\text{CH}(\text{CH}_3)_2\). 3. Assign positions: The number 4 indicates the position of the isopropyl group on the main chain. 4. Draw the full structural formula: \( \text{CH}_3-\text{CH}_2-\text{CH}_2-\mathrm{C}(\mathrm{CH}_3)_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_3\)

(d) 2,3,4-trimethylheptane

1. Identify the main chain: 'Heptane' indicates a 7-carbon main chain. 2. Identify branching groups: 'Trimethyl' indicates 3 methyl (\(\text{CH}_3\)) groups are branched off the main chain. 3. Assign positions: The numbers 2, 3, and 4 indicate the positions of the methyl groups on the main chain. 4. Draw the full structural formula: \( \text{CH}_3-\text{C}(\text{CH}_3)-\text{C}(\text{CH}_3)-\text{C}(\text{CH}_3)-\text{CH}_2-\text{CH}_2-\text{CH}_3\)

Key concepts

Organic Chemistry

Organic chemistry is the study of carbon-containing compounds and their properties. Most of the compounds in organic chemistry include carbon and hydrogen, forming the backbone of organic molecules.
Alkanes are a key class of organic compounds characterized by single carbon-carbon bonds and a saturated chemical structure. They are the simplest family of hydrocarbons, primarily made of carbon and hydrogen atoms.
Alkanes are critical to understanding the foundations of organic chemistry, as they set the basis for naming conventions and structural analysis of more complex molecules.

• Alkanes are saturated hydrocarbons.
• They follow the general formula \( ext{C}_n ext{H}_{2n+2} \).
• Alkanes can be linear or branched structures.

The ability to recognize and draw alkanes is essential for anyone venturing into the vast world of organic chemistry applications.

Alkane Naming Conventions

The naming of alkanes is governed by systematic conventions laid out by the International Union of Pure and Applied Chemistry (IUPAC). This ensures that each compound's name signifies its structure and composition rather than being arbitrary.
When naming alkanes, the longest continuous chain of carbon atoms is identified, which defines the main chain or parent skeleton of the molecule. The other segments or branches of the molecule are named according to their carbon content, modified with appropriate prefixes.

• The number of carbon atoms in the main chain is reflected in the parent name like methane (1 carbon), ethane (2 carbons), propane (3 carbons), etc.
• Branching groups like 'methyl' (one carbon), 'ethyl' (two carbons) are included as prefixes, accompanied by numbers designating their position along the main chain.
• Numbers are separated by commas; numbers and names are separated by hyphens.

Understanding these naming conventions helps in accurately identifying and communicating the structure of the compound.

Structural Drawing Techniques

Drawing structural formulas in organic chemistry involves visually representing the arrangement of atoms within a molecule.
This includes indicating how atoms are bonded and highlighting branching points for a clearer understanding of the compound's geometry and symmetry.
In structural formulas, each line represents a bond between atoms, and specific attention is paid to ensure substituents, such as methyl or isopropyl groups, are correctly positioned.

• Each bond is shown explicitly, capturing the connectivity of the compound.
• Branches are depicted to show their connection to the main carbon chain.
• Simplified depictions use condensed formats like \( ext{C}( ext{CH}_3)_2 \) to indicate branching groups.

A well-drafted structural formula allows for a straightforward interpretation of complex organic molecules, facilitating easier discussion and analysis of their chemical properties.