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

Molecular Geometry

Organic Chemistry

1. A Review of General Chemistry

Molecular Geometry

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2:08 minutes

Problem 31d

Textbook Question

Predict the approximate size of the following bond angles.
(d) the C—N—C bond angle in a quaternary ammonium salt

Verified step by step guidance

Review the structure of a quaternary ammonium salt. A quaternary ammonium salt has a central nitrogen atom bonded to four alkyl or aryl groups and carries a positive charge. The nitrogen is sp³ hybridized, meaning it forms four sigma bonds.

Recall the ideal bond angles for sp³ hybridized atoms. In an sp³ hybridized geometry, the electron pairs are arranged in a tetrahedral shape to minimize electron pair repulsion. The ideal bond angle for a tetrahedral geometry is approximately 109.5°.

Consider the effect of the positive charge on the nitrogen atom. The positive charge does not significantly alter the geometry because all four substituents are bonded to the nitrogen atom, and there are no lone pairs to cause additional repulsion.

Compare this situation to other sp³ hybridized atoms. Since there are no lone pairs on the nitrogen atom in a quaternary ammonium salt, the bond angles are expected to be close to the ideal tetrahedral angle of 109.5°.

Conclude that the C—N—C bond angle in a quaternary ammonium salt is approximately 109.5°, as the geometry is determined by the sp³ hybridization and the absence of lone pairs on the nitrogen atom.

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Key Concepts

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

Hybridization

Hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals that can accommodate bonding. In the case of quaternary ammonium salts, the nitrogen atom typically undergoes sp³ hybridization, leading to the formation of four equivalent sp³ hybrid orbitals that arrange themselves in a tetrahedral geometry.

Bond Angles

Bond angles are the angles formed between two bonds that share a common atom. In a tetrahedral arrangement, such as that found in quaternary ammonium salts, the ideal bond angle is approximately 109.5 degrees. However, the presence of different substituents can slightly alter these angles.

Steric Effects

Steric effects refer to the influence of the spatial arrangement of atoms on the reactivity and stability of a molecule. In quaternary ammonium salts, the bulky alkyl groups attached to the nitrogen can create steric hindrance, which may affect the bond angles slightly, but the overall tetrahedral geometry remains dominant.