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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1:59 minutes

Problem 31b

Textbook Question

Predict the approximate size of the following bond angles.
(b) the C—N—C bond angle in a secondary amine

Verified step by step guidance

Step 1: Recall the concept of hybridization and molecular geometry. In a secondary amine, the nitrogen atom is sp³ hybridized because it forms three sigma bonds (two C—N bonds and one N—H bond) and has one lone pair of electrons.

Step 2: Understand the effect of lone pairs on bond angles. Lone pairs occupy more space than bonding pairs due to their higher electron density, which causes bond angles to be slightly smaller than the ideal tetrahedral angle of 109.5°.

Step 3: Consider the geometry around the nitrogen atom. The molecular geometry is trigonal pyramidal due to the lone pair on nitrogen, which pushes the bonded atoms closer together.

Step 4: Predict the approximate bond angle. The C—N—C bond angle in a secondary amine will be slightly less than 109.5°, typically around 107°, due to the repulsion caused by the lone pair.

Step 5: Relate this prediction to real-world observations. Bond angles in molecules with lone pairs are consistently smaller than the ideal tetrahedral angle, and this trend is observed in secondary amines as well.

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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 a secondary amine, the nitrogen atom typically undergoes sp3 hybridization, leading to a tetrahedral arrangement of electron pairs, which influences the bond angles around the nitrogen.

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) Theory is used to predict the geometry of molecules based on the repulsion between electron pairs. For a secondary amine, the presence of lone pairs on the nitrogen atom and the bonding pairs with carbon atoms will determine the bond angles, typically resulting in angles close to 109.5 degrees.

Bond Angles in Organic Molecules

Bond angles in organic molecules are influenced by the type of hybridization and the steric effects of surrounding atoms. In secondary amines, the C—N—C bond angle is generally expected to be around 109.5 degrees due to the tetrahedral geometry associated with sp3 hybridization, although it may be slightly affected by the presence of lone pairs.

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Related Practice

Textbook Question

Predict the approximate bond angles for the following:

c. the C—C—N bond angle in CH₃C≡N

d. the C—C—N bond angle in CH₃CH₂NH₂

Textbook Question

Circle the coplanar atoms in the following structure:

Textbook Question

For each of the following compounds and ions,

1. Draw a Lewis structure.

2. Show the kinds of orbitals that overlap to form each bond.

3. Give approximate bond angles around each atom except hydrogen.

c. CH₂=N–CH₃

Textbook Question

You drew the Lewis structures of the following compounds and ion in Assessment 2.32. Predict their shapes around the central atom based on the Lewis structure.

(d) CO₃^2-

Textbook Question

You drew the Lewis structures of the following compounds and ion in Assessment 2.32. Predict their shapes around the central atom based on the Lewis structure.

Textbook Question

Describe the orbitals used in bonding and the bond angles in the following compounds:

a. CH₃O^-

Textbook Question

What is the hybridization of all the atoms (other than hydrogen) in each of the following?

What are the bond angles around each atom?

c. ^-CH₃

d. ⋅CH₃

Textbook Question

For each of the following molecules, indicate the hybridization of each carbon and give the approximate values of all the bond angles:

b. CH₃CH═CH₂

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Predict the approximate size of the following bond angles.(b) the C—N—C bond angle in a secondary amine

Key Concepts

Hybridization

VSEPR Theory

Bond Angles in Organic Molecules

Watch next

Predict the approximate size of the following bond angles.
(b) the C—N—C bond angle in a secondary amine