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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1:07 minutes

Problem 21

Textbook Question

Suggest a mechanism for the reaction shown in Figure 16.30 using IZnCH₂I as the cyclopropanating reagent.

Verified step by step guidance

Identify the starting materials and the reagent: The reaction involves a substrate with a double bond and the reagent IZnCH₂I, which is a cyclopropanating agent.

Understand the role of IZnCH₂I: This reagent is used to form cyclopropane rings by inserting a CH₂ group across a double bond. The zinc (Zn) acts as a stabilizing metal center that facilitates the transfer of the CH₂ group.

Initiate the mechanism by forming a carbenoid: The IZnCH₂I reagent can be thought of as generating a carbenoid species, which is a reactive intermediate similar to a carbene but stabilized by the metal (Zn).

Propose the interaction with the double bond: The carbenoid species will interact with the π electrons of the double bond in the substrate. This interaction leads to the formation of a three-membered cyclopropane ring.

Conclude the mechanism: The cyclopropanation is completed when the CH₂ group is inserted across the double bond, resulting in the formation of a cyclopropane ring. The zinc iodide (ZnI₂) is released as a byproduct.

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Key Concepts

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

Cyclopropanation Reaction

Cyclopropanation is a chemical reaction that introduces a cyclopropane ring into a molecule. It typically involves the addition of a carbene or carbenoid to an alkene, forming a three-membered ring. Understanding the nature of the cyclopropanating reagent, such as IZnCH₂I, is crucial for predicting the reaction pathway and the stereochemistry of the product.

Carbenoid Reagents

Carbenoid reagents, like IZnCH₂I, are compounds that mimic the behavior of carbenes, which are highly reactive species with a divalent carbon atom. These reagents facilitate the formation of cyclopropane rings by transferring a CH₂ group to an alkene. Recognizing the properties and reactivity of carbenoids helps in understanding their role in cyclopropanation reactions.

Reaction Mechanism

A reaction mechanism outlines the step-by-step process by which reactants transform into products, detailing the movement of electrons and the formation and breaking of bonds. For cyclopropanation using IZnCH₂I, the mechanism involves the generation of a carbenoid intermediate, its interaction with the alkene, and the subsequent formation of the cyclopropane ring. Understanding mechanisms is essential for predicting reaction outcomes and designing synthetic pathways.

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When it is strongly heated, ethyl diazoacetate decomposes to give nitrogen gas and a carbene. Draw a Lewis structure of the carbene.

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

(c)

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.

(f) Cyclopropanation of (E)- and (Z)-3-methylhex-3-ene gives two different products. Rationalize this outcome.

Textbook Question

Two chemists at Dupont found that ICH₂ZnI is better than diazomethane at converting a C=C bond to a cylcopropane ring. Propose a mechanism for the reaction, now known as the Simmons–Smith reaction in their honor.

Multiple Choice

What is the formal charge on the carbon of the following carbene?

Multiple Choice

Predict the major, organic product of the following reaction.

Multiple Choice

Predict the major, organic product for the following reaction.

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