Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

2. Molecular Representations

Intermolecular Forces

Organic Chemistry

2. Molecular Representations

Intermolecular Forces

Previous problemNext problem

4:50 minutes

Problem 42b

Textbook Question

In each pair of compounds, which compound has the higher boiling point? Explain your reasoning.
b. nonane or 2-methylheptane

Verified step by step guidance

Identify the structural differences between nonane and 2-methylheptane. Nonane is a straight-chain alkane with nine carbon atoms, while 2-methylheptane is a branched alkane with a total of eight carbon atoms and one methyl group attached to the second carbon.

Understand the concept of boiling point in relation to molecular structure. Boiling point is influenced by intermolecular forces, primarily van der Waals forces in alkanes. The strength of these forces is affected by the surface area of the molecule and the ability to pack closely together.

Consider the impact of molecular branching on boiling point. Straight-chain alkanes like nonane have a larger surface area and can pack more efficiently, leading to stronger van der Waals forces compared to branched alkanes like 2-methylheptane.

Evaluate the molecular weight and size. Both compounds have similar molecular weights, but the linear structure of nonane allows for more effective intermolecular interactions than the branched structure of 2-methylheptane.

Conclude that nonane, with its straight-chain structure, will have a higher boiling point than 2-methylheptane due to stronger van der Waals forces resulting from its larger surface area and better packing efficiency.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Boiling Point

The boiling point of a compound is the temperature at which its vapor pressure equals the atmospheric pressure, causing it to transition from liquid to gas. It is influenced by molecular weight, intermolecular forces, and molecular structure. Stronger intermolecular forces, such as hydrogen bonding or van der Waals forces, typically result in higher boiling points.

Intermolecular Forces

Intermolecular forces are the forces that hold molecules together, affecting physical properties like boiling points. In hydrocarbons, van der Waals forces (dispersion forces) are predominant. Linear molecules, like nonane, have more surface area for these forces to act upon compared to branched molecules like 2-methylheptane, often resulting in higher boiling points for linear structures.

Molecular Structure

Molecular structure refers to the arrangement of atoms within a molecule, impacting its physical properties. Linear molecules, such as nonane, tend to have higher boiling points than their branched counterparts, like 2-methylheptane, due to increased surface area allowing stronger van der Waals interactions. Branching reduces these interactions, often lowering the boiling point.