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

21. Aldehydes and Ketones: Nucleophilic Addition

Wittig Reaction

Organic Chemistry

21. Aldehydes and Ketones: Nucleophilic Addition

Wittig Reaction

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3:19 minutes

Problem 49a(1)

Textbook Question

What two sets of reagents (each consisting of a carbonyl compound and phosphonium ylide) can be used for the synthesis of the following alkene?
1.

Verified step by step guidance

Step 1: Understand the problem. The question involves the Wittig reaction, which is a method to synthesize alkenes by reacting a carbonyl compound (aldehyde or ketone) with a phosphonium ylide. The goal is to determine two possible sets of reagents (carbonyl compound and ylide) that could produce the given alkene.

Step 2: Analyze the structure of the target alkene. Identify the two groups attached to the double bond (R1 and R2) and determine how the molecule can be split into two fragments: one derived from the carbonyl compound and the other from the ylide.

Step 3: Assign one fragment to the carbonyl compound and the other to the ylide. Recall that the carbonyl compound contributes the carbonyl carbon and its attached group, while the ylide contributes the carbon atom of the double bond and its attached group. Write the structures of the two reagents for the first set.

Step 4: Reverse the roles of the fragments. Assign the other fragment to the carbonyl compound and the remaining fragment to the ylide. Write the structures of the two reagents for the second set.

Step 5: Verify the proposed reagents. Ensure that each set of reagents, when reacted via the Wittig reaction, would produce the target alkene. This involves confirming that the connectivity and stereochemistry (if applicable) match the given alkene.

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Key Concepts

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

Carbonyl Compounds

Carbonyl compounds are organic molecules that contain a carbon atom double-bonded to an oxygen atom (C=O). They are key intermediates in various organic reactions, including nucleophilic addition and condensation reactions. Understanding the reactivity of carbonyl compounds is essential for predicting the outcomes of synthetic pathways, such as those involving the formation of alkenes.

Phosphonium Ylides

Phosphonium ylides are reactive intermediates formed by the deprotonation of phosphonium salts, which contain a positively charged phosphorus atom. They are crucial in the Wittig reaction, where they react with carbonyl compounds to form alkenes. The stability and structure of the ylide influence the selectivity and yield of the resulting alkene, making them vital for synthetic strategies in organic chemistry.

Wittig Reaction

The Wittig reaction is a chemical reaction that allows for the synthesis of alkenes from carbonyl compounds and phosphonium ylides. This reaction involves the formation of an alkene through the nucleophilic attack of the ylide on the carbonyl carbon, followed by the elimination of a phosphine oxide. Mastery of this reaction is essential for organic chemists, as it provides a powerful method for constructing double bonds in complex molecules.

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Related Practice

Textbook Question

Like other strong nucleophiles, triphenylphosphine attacks and opens epoxides. The initial product (a betaine) quickly cyclizes to an oxaphosphetane that collapses to an alkene and triphenylphosphine oxide.

(a) Show each step in the reaction of trans-2,3-epoxybutane with triphenylphosphine to give but-2-ene. What is the stereochemistry of the double bond in the product?

Textbook Question

(b) Show how this sequence might be used to convert cis-cyclooctene to trans-cyclooctene.

Textbook Question

Show how you would accomplish the following syntheses efficiently and in good yield. You may use any necessary reagents.

(e)

Textbook Question

Show how you would accomplish the following synthetic conversions efficiently and in good yield. You may use any necessary additional reagents and solvents.

(h)

Textbook Question

Suggest the appropriate carbonyl and Wittig reagent to make the following alkenes.

a. (E)-7-methylnon-4-en-3-one

Multiple Choice

Determine the carbonyl and ylide that formed the following product.

Multiple Choice

Predict the major, organic product for the following reaction.

Textbook Question

Trimethylphosphine is a stronger nucleophile than triphenylphosphine, but it is rarely used to make ylides. Why is trimethylphosphine unsuitable for making most phosphorus ylides?

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What two sets of reagents (each consisting of a carbonyl compound and phosphonium ylide) can be used for the synthesis of the following alkene?1.

Key Concepts

Carbonyl Compounds

Phosphonium Ylides

Wittig Reaction

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What two sets of reagents (each consisting of a carbonyl compound and phosphonium ylide) can be used for the synthesis of the following alkene?
1.