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

Ozonolysis

Organic Chemistry

10. Addition Reactions

Ozonolysis

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3:11 minutes

Problem 54c,d

Textbook Question

Professor Patrick Dussault (University of Nebraska at Lincoln) has developed an alternative to the standard two-step ozonolysis procedure requiring reduction of the ozonide in a second step. He uses 2 to 3 equivalents of pyridine, a mildly basic organic solvent, in a one-step process (Organic Letters, 2012, 14, 2242). Show the products you expect from the following examples.
(c)
(d)

Verified step by step guidance

Step 1: Understand the reaction mechanism. Ozonolysis is a reaction where an alkene reacts with ozone (O₃) to form an ozonide intermediate, which is then reduced to yield carbonyl compounds (aldehydes or ketones). In this alternative method, pyridine is used as a reducing agent in a one-step process.

Step 2: Analyze the structure of the alkene in the given examples (c and d). Identify the double bond(s) in the molecule, as these are the sites where ozonolysis will occur.

Step 3: Break the double bond(s) in the alkene symmetrically. Replace each carbon-carbon double bond with two carbonyl groups (C=O). For each carbon in the double bond, determine whether it will form an aldehyde or a ketone based on the substituents attached to it.

Step 4: Consider the role of pyridine. Pyridine is a mild base and helps stabilize the reaction environment, ensuring that the ozonide intermediate is reduced directly to the carbonyl products without requiring a second step.

Step 5: Draw the final products for each example (c and d) by replacing the double bonds with the appropriate carbonyl groups. Ensure that the connectivity of the molecule is preserved and that the products are consistent with the ozonolysis mechanism.

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Key Concepts

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

Ozonolysis

Ozonolysis is a reaction involving the cleavage of alkenes or alkynes using ozone (O3) to form carbonyl compounds, typically aldehydes or ketones. In the standard procedure, the reaction occurs in two steps: first, ozone adds to the double bond to form an ozonide, which is then reduced in a second step, often using a reducing agent like zinc or dimethyl sulfide. Understanding this process is crucial for predicting the products of ozonolysis reactions.

Pyridine as a Solvent

Pyridine is a basic, aromatic organic compound that is often used as a solvent in organic reactions due to its ability to stabilize reactive intermediates. In the context of ozonolysis, pyridine can facilitate the reaction by acting as a nucleophile, helping to convert the ozonide into carbonyl products in a one-step process. Its mild basicity allows it to participate without overly aggressive reactivity, making it suitable for delicate transformations.

Reaction Mechanism

A reaction mechanism describes the step-by-step sequence of elementary reactions by which overall chemical change occurs. In ozonolysis, understanding the mechanism is essential to predict the structure of the products formed. The mechanism involves the formation of a cyclic ozonide intermediate, which can rearrange or react with the solvent (in this case, pyridine) to yield the final carbonyl compounds, highlighting the importance of both the starting materials and the reaction conditions.

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Related Practice

Textbook Question

Give structures of the alkenes that would give the following products upon ozonolysis–reduction.

(c)

Textbook Question

Using 1,2-dimethylcyclohexene as your starting material, show how you would synthesize the following compounds. (Once you have shown how to synthesize a compound, you may use it as the starting material in any later parts of this problem.) If a chiral product is shown, assume that it is part of a racemic mixture.

(i)

Textbook Question

Show how you would synthesize each compound using methylenecyclohexane as your starting material.

(d)

Textbook Question

Ozonolysis can be applied selectively to different types of carbon–carbon double bonds. The compound shown below contains two vinyl ether double bonds, which are electron-rich because of the electron-donating alkoxy groups. Ozone reacts more quickly with electron-rich double bonds and more slowly with hindered double bonds. At −78 °C, this compound quickly adds two equivalents of ozone. Immediate reduction of the ozonide gives a good yield of a single product. Show the expected ozonolyis product, and label the functional groups produced, some of which are not typical from ozonolysis of simple alkenes.

Textbook Question

Predict the major products of the following reactions.

(c)

(d) 1-ethylcycloheptene + ozone, then (CH₃)₂S

Textbook Question

What products are formed when the following compounds react with ozone and then with dimethyl sulfide?

Textbook Question

Ozonolysis of an alkene, followed by treatment with dimethyl sulfide, forms the following product(s). Identify the alkene in each case.

Textbook Question

What is the major product of the reaction of 2-methyl-2-butene with each of the following reagents?

d. O₃, −78 °C, followed by (CH₃)₂S

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