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

10. Addition Reactions

Carbene

Organic Chemistry

10. Addition Reactions

Carbene

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Problem 79h

Textbook Question

In addition to radicals, anions, and cations, a fourth class of reactive intermediates is carbenes. A neutral species, the simplest carbene has a molecular formula of CH₂.
(h) Of the reactions studied here in Chapter 8, cyclopropanation is most similar to which?

Verified step by step guidance

Carbenes are neutral reactive intermediates with a divalent carbon atom that has two nonbonding electrons. The simplest carbene is methylene (CH₂). Carbenes can participate in various reactions, including cyclopropanation.

Cyclopropanation is a reaction where a carbene reacts with an alkene to form a cyclopropane ring. This involves the addition of the carbene across the double bond of the alkene.

To determine which reaction cyclopropanation is most similar to, consider the mechanism. Cyclopropanation involves the addition of a species (the carbene) to a double bond, forming a three-membered ring.

Compare this to other reactions studied in Chapter 8. For example, electrophilic addition reactions involve the addition of an electrophile to a double bond, which is conceptually similar to the addition of a carbene to a double bond in cyclopropanation.

Thus, cyclopropanation is most similar to electrophilic addition reactions, as both involve the addition of a reactive species to a double bond, leading to the formation of a new product.

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Key Concepts

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

Carbenes

Carbenes are neutral reactive intermediates that contain a carbon atom with only six valence electrons, making them highly reactive. The simplest carbene, methylene (CH₂), can participate in various chemical reactions, including addition to double bonds. Understanding carbenes is crucial for predicting their behavior in organic reactions, particularly in cyclopropanation.

Cyclopropanation

Cyclopropanation is a chemical reaction that involves the formation of a cyclopropane ring by the addition of a carbene to a double bond. This reaction is significant in organic synthesis as it allows for the creation of three-membered rings, which are valuable intermediates in the synthesis of more complex molecules. Recognizing the mechanism of cyclopropanation helps in comparing it to other reactions.

Reactivity of Intermediates

The reactivity of intermediates like carbenes, radicals, anions, and cations is fundamental in organic chemistry. Each type of intermediate has distinct properties and reactivity patterns that influence the course of chemical reactions. Understanding these differences is essential for predicting the outcomes of reactions, including which reactions are similar to cyclopropanation.

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Related Practice

Textbook Question

Predict the product of the following reactions.

(b)

Textbook Question

The following transformation is used as an early step in the synthesis of cilastatin, a drug used to counter antibiotic resistance. Identify a possible reagent for this step.

Textbook Question

Predict the product of the following reactions.

(a)

Textbook Question

Cyclopropanation using any of the reagents discussed here is stereospecific.

(b) Draw a reaction coordinate diagram for cyclopropanation.

Textbook Question

To determine the stereochemistry of curacin A by synthesis, it would have been necessary to prepare all stereoisomers of the C₁₇―C₂₀ cyclopropane fragment. How would the reaction in Figure 16.30 be modified to produce the other stereoisomers shown here?

Textbook Question

Nitrogen-containing heterocycles form particularly stable carbenes and are commonly used as ligands in organometallic chemistry. (a) Why is the carbene shown particularly stable? [It may be helpful to draw the molecular orbital picture.]

Textbook Question

The reaction of an alkene with diazomethane forms a cyclopropane ring. Propose a mechanism for the reaction. (Hint: It is a concerted reaction.)

Textbook Question

Show how you would accomplish each of the following synthetic conversions.

a. trans-but-2-ene → trans-1,2-dimethylcyclopropane

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