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

14. Synthetic Techniques

Alkynide Alkylation

Organic Chemistry

14. Synthetic Techniques

Alkynide Alkylation

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3:56 minutes

Problem 11d

Textbook Question

Show how you would accomplish the following synthetic conversions. You may use any additional reagents and solvents you need.
(d)

Verified step by step guidance

Step 1: Begin with the starting material, benzaldehyde (PhCHO). To introduce the alkyne functionality, perform a nucleophilic addition reaction using ethynylmagnesium bromide (C≡CHMgBr), a Grignard reagent. This will add the ethynyl group to the carbonyl carbon, forming an alcohol intermediate.

Step 2: After the addition of the ethynyl group, the intermediate will be a secondary alcohol with the structure PhCH(OH)C≡CH. This step involves hydrolysis of the Grignard addition product using water or dilute acid.

Step 3: To extend the alkyne chain, perform an alkylation reaction. Deprotonate the terminal alkyne (C≡CH) using a strong base such as sodium amide (NaNH2) to generate the acetylide anion (C≡C⁻). Then, react this anion with ethyl bromide (CH3CH2Br) to introduce the ethyl group, forming PhCH(OH)C≡CCH2CH3.

Step 4: Ensure stereochemical integrity and verify the product structure. The hydroxyl group remains intact, and the alkyne chain is extended as desired. Use spectroscopic techniques like NMR or IR to confirm the presence of the alcohol and alkyne functionalities.

Step 5: Purify the final product using appropriate methods such as column chromatography or recrystallization to isolate PhCH(OH)C≡CCH2CH3 in high yield and purity.

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Key Concepts

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

Aldol Condensation

Aldol condensation is a key reaction in organic chemistry where aldehydes or ketones with alpha-hydrogens react in the presence of a base to form beta-hydroxy aldehydes or ketones. This reaction can lead to the formation of larger carbon skeletons through the formation of carbon-carbon bonds, which is essential for synthesizing complex molecules.

Alkyne Formation

The formation of alkynes typically involves the elimination of small molecules from alkenes or the dehydrohalogenation of alkyl halides. In this context, the conversion of a compound to an alkyne requires specific reagents, such as strong bases, to facilitate the removal of hydrogen or halogen atoms, resulting in the formation of a triple bond.

Reagent Selection

Choosing the appropriate reagents and solvents is crucial in organic synthesis to ensure the desired reaction occurs efficiently. For the conversion of PhCHO to the target compound, reagents such as sodium hydroxide for aldol condensation and strong bases like sodium amide for alkyne formation may be necessary to achieve the desired transformations while controlling reaction conditions.

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