Question

Name all unbranched ether and alcohol isomers with formula \(\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O},\) and write their structural formulas.

Short answer

There are 5 unbranched isomers: 3 alcohols and 2 ethers.

Step-by-step solution

Understanding the Molecular Formula

The molecular formula given is \( \mathrm{C}_5\mathrm{H}_{12}\mathrm{O} \). This indicates that the compound contains 5 carbon atoms, 12 hydrogen atoms, and 1 oxygen atom. We need to explore both alcohols (\(-\mathrm{OH}\) group) and ethers (an oxygen atom connected between two carbon groups).

Identifying Alcohol Isomers

To find alcohol isomers, we attach the \(-\mathrm{OH}\) group to different carbon atoms across a 5-carbon chain. The possible unbranched alcohols are: 1. 1-pentanol: \( \mathrm{CH}_3(\mathrm{CH}_2)_3\mathrm{CH}_2\mathrm{OH} \)2. 2-pentanol: \( \mathrm{CH}_3(\mathrm{CH}_2)_2\mathrm{CH}\mathrm{(OH)}\mathrm{CH}_3 \)3. 3-pentanol: \( \mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}(\mathrm{OH})\mathrm{CH}_2\mathrm{CH}_3 \)

Identifying Ether Isomers

For ether isomers, the oxygen atom must lie between carbon groups. For a 5-carbon atom structure, the following unbranched ethers are possible:1. Methyl butyl ether: \( \mathrm{CH}_3\mathrm{OCH}_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_3 \)2. Ethyl propyl ether: \( \mathrm{CH}_3\mathrm{CH}_2\mathrm{OCH}_2\mathrm{CH}_2\mathrm{CH}_3 \)

Counting Total Isomers

Combining both alcohol and ether possibilities, we have a total of 5 unbranched isomers: 3 alcohol isomers and 2 ether isomers.

Key concepts

Alcohol Isomers

Alcohol isomers are compounds that have the same molecular formula but differ in the placement of the hydroxyl group \((-\mathrm{OH})\) on the carbon chain. For the formula \(\mathrm{C}_5\mathrm{H}_{12}\mathrm{O}\), we explore the possibilities where the \(-\mathrm{OH}\) group is attached to different carbon atoms in a linear or open chain structure.
1. **1-Pentanol**: This is the simplest unbranched alcohol isomer. The hydroxyl group is attached to the first carbon in the chain. Its structural formula is \(\mathrm{CH}_3(\mathrm{CH}_2)_3\mathrm{CH}_2\mathrm{OH}\).
2. **2-Pentanol**: Here, the hydroxyl group is attached to the second carbon atom in the chain. Its structural formula is \(\mathrm{CH}_3(\mathrm{CH}_2)_2\mathrm{CH}(\mathrm{OH})\mathrm{CH}_3\).
3. **3-Pentanol**: In this case, the hydroxyl group is attached to the third carbon atom. Its structure is \(\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}(\mathrm{OH})\mathrm{CH}_2\mathrm{CH}_3\).
Different placement of the \( -\mathrm{OH}\) group results in different chemical and physical properties, even though the molecular formula remains the same.

Ether Isomers

Ether isomers are compounds where an oxygen atom is sandwiched between two carbon groups in the chain. For \(\mathrm{C}_5\mathrm{H}_{12}\mathrm{O}\), we can form these ether isomers:
1. **Methyl Butyl Ether**: The oxygen atom is placed between a methyl group (\(\mathrm{CH}_3\)) and a butyl group (\(\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_3\)). This results in the structure: \(\mathrm{CH}_3\mathrm{OCH}_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_3\).
2. **Ethyl Propyl Ether**: In this isomer, the oxygen atom sits between an ethyl group (\(\mathrm{CH}_3\mathrm{CH}_2\)) and a propyl group (\(\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_3\)). The structural formula is \(\mathrm{CH}_3\mathrm{CH}_2\mathrm{OCH}_2\mathrm{CH}_2\mathrm{CH}_3\).
Despite having the same molecular formula, the arrangement of atoms in ether isomers influences the compound's boiling point, solubility, and reactivity. The position of the oxygen atom significantly affects these properties.

Structural Formulas

Structural formulas provide a graphical representation of the arrangement of atoms in a molecule. They display how atoms are connected in a molecule, using lines to denote chemical bonds.
For isomers with the formula \(\mathrm{C}_5\mathrm{H}_{12}\mathrm{O}\), structural formulas are crucial in differentiating them because they reveal the specific connectivity of atoms, which defines each isomer's identity and properties.
In alcohol isomers, the hydroxyl group \((-\mathrm{OH}\)) is shown connecting directly to the carbon atom, whereas in ether isomers, the oxygen bridges two carbon chains.

• **1-Pentanol**: \(\mathrm{CH}_3(\mathrm{CH}_2)_3\mathrm{CH}_2\mathrm{OH}\)
• **2-Pentanol**: \(\mathrm{CH}_3(\mathrm{CH}_2)_2\mathrm{CH}(\mathrm{OH})\mathrm{CH}_3\)
• **3-Pentanol**: \(\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}(\mathrm{OH})\mathrm{CH}_2\mathrm{CH}_3\)
• **Methyl Butyl Ether**: \(\mathrm{CH}_3\mathrm{OCH}_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_3\)
• **Ethyl Propyl Ether**: \(\mathrm{CH}_3\mathrm{CH}_2\mathrm{OCH}_2\mathrm{CH}_2\mathrm{CH}_3\)

Structural formulas are valuable as they translate the abstract chemical formula into a detailed layout that can be easily understood by chemists trying to determine the properties or reactivity of a substance.