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 Orbitals

Organic Chemistry

1. A Review of General Chemistry

Molecular Orbitals

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3:58 minutes

Problem 26a,b

Textbook Question

Indicate the kind of molecular orbital (σ, σ, π, or π) that results when the two atomic orbitals are combined:
a. <IMAGE>
b. <IMAGE>

Verified step by step guidance

Step 1: Analyze the image labeled 'A'. The two atomic orbitals are overlapping end-to-end along the internuclear axis. This type of overlap typically results in the formation of a sigma (σ) molecular orbital.

Step 2: Consider the bonding interaction in 'A'. Since the lobes of the orbitals are overlapping constructively (same phase), this indicates the formation of a bonding sigma (σ) orbital.

Step 3: Analyze the image labeled 'B'. The two atomic orbitals are overlapping end-to-end along the internuclear axis, but the lobes are overlapping destructively (opposite phases). This type of interaction results in the formation of an antibonding sigma star (σ*) molecular orbital.

Step 4: Understand the concept of molecular orbitals. Sigma (σ) orbitals are formed by constructive overlap of atomic orbitals along the internuclear axis, while sigma star (σ*) orbitals are formed by destructive overlap.

Step 5: Summarize the results: 'A' corresponds to a bonding sigma (σ) orbital, and 'B' corresponds to an antibonding sigma star (σ*) orbital.

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Key Concepts

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

Molecular Orbitals

Molecular orbitals (MOs) are formed when atomic orbitals combine during the bonding process. They can be classified into bonding and antibonding orbitals. Bonding orbitals, such as σ and π, stabilize the molecule, while antibonding orbitals, like σ* and π*, destabilize it. Understanding the shapes and orientations of these orbitals is crucial for predicting molecular behavior.

Bonding and Antibonding Orbitals

Bonding orbitals (σ and π) result from the constructive interference of atomic orbitals, leading to increased electron density between nuclei, which stabilizes the molecule. Antibonding orbitals (σ* and π*) arise from destructive interference, resulting in decreased electron density between nuclei and increased energy. Identifying whether the combination of atomic orbitals leads to bonding or antibonding orbitals is essential for understanding molecular stability.

Orbital Symmetry and Orientation

The symmetry and orientation of atomic orbitals play a critical role in determining the type of molecular orbital formed. For example, the overlap of two p orbitals can create π or π* orbitals depending on their relative orientation. Recognizing how the shapes of orbitals interact helps predict the resulting molecular orbital type, which is key to answering the question posed.

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Related Practice

Textbook Question

Draw orbital pictures of the pi bonding in the following compounds:

e. CH₃CH=C=CHCH₃

Textbook Question

Draw orbital pictures of the pi bonding in the following compounds:

f. CH₃CH=NCH=C=O

Textbook Question

In this, and previous, chapters, we have seen 1,2-alkyl and 1,2-hydride shifts. If both are possible, as in the carbocation shown, which would you expect to occur? Explain your answer.

Textbook Question

Draw orbital pictures of the pi bonding in the following compounds:

a. CH₃COCH₃

b. HCN

Textbook Question

Draw the following orbitals:

a. 3s orbital

b. 4s orbital

c. 3p orbital

Textbook Question

A molecular orbital diagram is shown for the C―Cl bond in chloromethane. If two more electrons were added to chloromethane, where would the electrons go?

<IMAGE>

Textbook Question

There is free rotation around the C―C bond in ethane. There is an extremely high barrier to rotation around the C=C bond in in ethene. Explain.

Textbook Question

Looking ahead in Chapter 4, we explain that molecules like CH₃⁺ are Lewis acids or electron pair acceptors. Into which orbital would the new electron pair go?

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Indicate the kind of molecular orbital (σ, σ*, π, or π*) that results when the two atomic orbitals are combined: a. <IMAGE>b. <IMAGE>

Key Concepts

Molecular Orbitals

Bonding and Antibonding Orbitals

Orbital Symmetry and Orientation

Watch next

Indicate the kind of molecular orbital (σ, σ, π, or π) that results when the two atomic orbitals are combined:
a. <IMAGE>
b. <IMAGE>