---
title: "The condensed structural formulas of three constitutional isomers with the molecular formula \\(\\text{C}_5\\text{H}_{12}\\) are shown in the table below.  | Compound | IUPAC name | Condensed structural formula | | :— | :— | :— | | X | Pentane | \\(\\text{CH}_3\\text{CH}_2\\text{CH}_2\\text{CH}_2\\text{CH}_3\\) | | Y | \\(2\\)-methylbutane | \\(\\text{CH}_3\\text{CH(CH}_3\\text{)CH}_2\\text{CH}_3\\) | | Z | \\(2,2\\)-dimethylpropane | \\(\\text{C(CH}_3)_4\\) |  Which of the following correctly ranks the isomers from highest to lowest normal boiling point and provides the correct justification?"
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url: "https://nerd-notes.com/ubq/123618/"
date_modified: "2026-09-28T12:01:47+00:00"
---

# The condensed structural formulas of three constitutional isomers with the molecular formula \(\text{C}_5\text{H}_{12}\) are shown in the table below.

| Compound | IUPAC name | Condensed structural formula |
| :— | :— | :— |
| X | Pentane | \(\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{CH}_3\) |
| Y | \(2\)-methylbutane | \(\text{CH}_3\text{CH(CH}_3\text{)CH}_2\text{CH}_3\) |
| Z | \(2,2\)-dimethylpropane | \(\text{C(CH}_3)_4\) |

Which of the following correctly ranks the isomers from highest to lowest normal boiling point and provides the correct justification?

The condensed structural formulas of three constitutional isomers with the molecular formula \(\text{C}_5\text{H}_{12}\) are shown in the table below.

| Compound | IUPAC name | Condensed structural formula |
| :--- | :--- | :--- |
| X | Pentane | \(\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{CH}_3\) |
| Y | \(2\)-methylbutane | \(\text{CH}_3\text{CH(CH}_3\text{)CH}_2\text{CH}_3\) |
| Z | \(2,2\)-dimethylpropane | \(\text{C(CH}_3)_4\) |

Which of the following correctly ranks the isomers from highest to lowest normal boiling point and provides the correct justification?

- **A.** \(\text{Pentane} > 2\text{-methylbutane} > 2,2\text{-dimethylpropane}\), because the elongated molecular shape of pentane provides a greater surface area of contact between molecules, resulting in stronger London dispersion forces.
- **B.** \(\text{Pentane} > 2\text{-methylbutane} > 2,2\text{-dimethylpropane}\), because pentane has a greater molar mass and a larger total number of electrons, resulting in a more polarizable electron cloud.
- **C.** \(2,2\text{-Dimethylpropane} > 2\text{-methylbutane} > \text{pentane}\), because the more compact, spherical shape of \(2,2\)-dimethylpropane packs electrons more densely, increasing its polarizability and dispersion forces.
- **D.** \(2,2\text{-Dimethylpropane} > 2\text{-methylbutane} > \text{pentane}\), because the branching in \(2,2\)-dimethylpropane produces an asymmetrical charge distribution and permanent dipole-dipole attractions.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123618/*