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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1:48 minutes

Problem 13

Textbook Question

Explain why HCl has a smaller dipole moment than HF, even though the H—Cl bond is longer than the H—F bond.

Verified step by step guidance

Dipole moment (μ) is calculated using the formula:

μ = q × d

, where

q

is the magnitude of the charge separation and

d

is the bond length. While bond length (

d

) is a factor, the magnitude of the charge separation (

q

) plays a critical role in determining the dipole moment.

The electronegativity of fluorine (F) is significantly higher than that of chlorine (Cl). This means that the electron density in the H—F bond is pulled more strongly toward the fluorine atom, resulting in a larger charge separation (

q

) compared to the H—Cl bond.

Although the H—Cl bond is longer than the H—F bond, the smaller charge separation in the H—Cl bond due to chlorine's lower electronegativity reduces its contribution to the dipole moment.

In the case of H—F, the combination of a shorter bond length and a much larger charge separation results in a higher dipole moment compared to H—Cl.

Thus, the smaller dipole moment of HCl is primarily due to the lower electronegativity of chlorine, which leads to a smaller charge separation, even though the bond length is longer.

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Key Concepts

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

Electronegativity

Electronegativity is a measure of an atom's ability to attract and hold onto electrons in a chemical bond. In the case of HCl and HF, fluorine is more electronegative than chlorine, which means that the H—F bond has a greater polarity. This difference in electronegativity contributes significantly to the dipole moment, as the more electronegative atom (F) pulls the electron density closer, creating a stronger dipole.

Bond Length and Dipole Moment

The dipole moment of a molecule is influenced by both the bond length and the difference in electronegativity between the bonded atoms. Although H—Cl is longer than H—F, the dipole moment is not solely determined by bond length. The greater electronegativity of fluorine results in a stronger dipole moment in HF, despite the shorter bond length, leading to a higher overall dipole moment compared to HCl.

Vector Nature of Dipole Moments

Dipole moments are vector quantities, meaning they have both magnitude and direction. The overall dipole moment of a molecule is the vector sum of the individual bond dipoles. In HCl, the bond dipole is less significant due to the lower electronegativity of chlorine compared to fluorine, resulting in a smaller net dipole moment for HCl, despite the longer bond length.