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

1. A Review of General Chemistry

Electronegativity

Organic Chemistry

1. A Review of General Chemistry

Electronegativity

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Problem 11a

Textbook Question

For each pair of compounds, predict the one with a higher boiling point. Which compounds have zero dipole moments?
a. cis-1,2-dichloroethene or cis-1,2-dibromoethene

Verified step by step guidance

Step 1: Understand that boiling point is influenced by molecular weight and intermolecular forces. Compounds with stronger intermolecular forces or higher molecular weights generally have higher boiling points.

Step 2: Compare the molecular weights of cis-1,2-dichloroethene and cis-1,2-dibromoethene. Bromine is heavier than chlorine, so cis-1,2-dibromoethene has a higher molecular weight.

Step 3: Consider the types of intermolecular forces present. Both compounds have dipole-dipole interactions due to the polar C-Cl and C-Br bonds, but the heavier bromine atoms in cis-1,2-dibromoethene contribute to stronger London dispersion forces.

Step 4: Predict that cis-1,2-dibromoethene will have a higher boiling point due to its higher molecular weight and stronger London dispersion forces.

Step 5: Determine the dipole moment. Both compounds are cis isomers, which means they have a net dipole moment due to the asymmetrical arrangement of the polar bonds. Therefore, neither compound has a zero dipole moment.

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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. Stronger forces, such as hydrogen bonding, dipole-dipole interactions, and London dispersion forces, result in higher boiling points. In comparing similar compounds, the size and polarizability of the molecules can also affect the boiling point, with larger, more polarizable molecules typically having higher boiling points.

Dipole Moment

A dipole moment occurs in a molecule when there is an uneven distribution of electron density, resulting in a partial positive and negative charge. Molecules with symmetrical structures, like trans isomers, often have zero dipole moments because the individual bond dipoles cancel each other out. In contrast, asymmetrical molecules, such as cis isomers, usually have a net dipole moment due to the non-cancellation of bond dipoles.

Cis and Trans Isomerism

Cis and trans isomerism is a type of stereoisomerism where molecules have the same formula but differ in the spatial arrangement of atoms around a double bond. In cis isomers, similar groups are on the same side of the double bond, often resulting in a net dipole moment. Trans isomers have similar groups on opposite sides, which can lead to a cancellation of dipole moments, affecting properties like boiling point and solubility.

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