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

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5:02 minutes

Problem 35

Textbook Question

Rank the following compounds from highest boiling to lowest boiling:

Verified step by step guidance

Step 1: Identify the functional groups in each compound. Compound A contains three amine groups (-NH2), compound B contains two amine groups, compound C contains one amine group, compound D contains one hydroxyl group (-OH), and compound E is a hydrocarbon with no polar functional groups.

Step 2: Understand the impact of functional groups on boiling points. Polar functional groups like -NH2 and -OH can form hydrogen bonds, which significantly increase boiling points. Hydrocarbons without polar groups have lower boiling points due to weaker intermolecular forces (London dispersion forces).

Step 3: Consider the number of hydrogen bonding sites. Compound A has the most hydrogen bonding sites due to three -NH2 groups, followed by compound B with two -NH2 groups, compound D with one -OH group, and compound C with one -NH2 group. Compound E has no hydrogen bonding capability.

Step 4: Evaluate molecular size and branching. Larger molecules with less branching tend to have higher boiling points due to increased surface area for intermolecular forces. Compound E is branched, which reduces its boiling point compared to straight-chain compounds.

Step 5: Rank the compounds based on boiling points. The order from highest boiling to lowest boiling is likely: A > B > D > C > E, considering the number of hydrogen bonding sites and the molecular structure.

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Key Concepts

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

Boiling Point and Intermolecular Forces

The boiling point of a compound is influenced by the strength of its intermolecular forces. Compounds with stronger forces, such as hydrogen bonding, dipole-dipole interactions, or ionic interactions, typically have higher boiling points. Understanding these forces helps predict the boiling point ranking of different compounds.

Hydrogen Bonding

Hydrogen bonding occurs when a hydrogen atom covalently bonded to a highly electronegative atom (like N or O) interacts with another electronegative atom. This type of bonding significantly increases the boiling point of compounds, as seen in alcohols and amines, due to the additional energy required to break these interactions during phase changes.

Molecular Structure and Polarity

The molecular structure and polarity of a compound affect its boiling point. Polar molecules tend to have higher boiling points than nonpolar molecules due to stronger dipole-dipole interactions. Additionally, branching in carbon chains can reduce boiling points by decreasing surface area and thus the strength of van der Waals forces.

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Related Practice

Textbook Question

Draw the hydrogen bonding that takes place between

c. a molecule of dimethyl ether and two molecules of water.

d. two molecules of trimethylamine and a molecule of water.

Textbook Question

Diethyl ether and butan-1-ol are isomers, and they have similar solubilities in water. Their boiling points are very different, however. Explain why these two compounds have similar solubility properties but dramatically different boiling points.

Textbook Question

N-Methylpyrrolidine has a boiling point of 81 °C, and piperidine has a boiling point of 106 °C.

b. Tetrahydropyran has a boiling point of 88 °C, and cyclopentanol has a boiling point of 141 °C. These two isomers have a boiling point difference of 53 °C. Explain why the two oxygen-containing isomers have a much larger boiling point difference than the two amine isomers.

Textbook Question

List each set of compounds in order of increasing boiling point.

a. hexane, octane, and decane

Textbook Question

Explain the following:

a. 1-Hexanol has a higher boiling point than 3-hexanol.

Textbook Question

Explain why

c. H₂O (100 °C) has a higher boiling point than HF 120 °C2.

d. HF 120 °C2 has a higher boiling point than NH₃ (-33 °C).

Textbook Question

Which of the following compounds forms hydrogen bonds between its molecules?