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

24. Enolate Chemistry: Reactions at the Alpha-Carbon

Enolate Alkylation and Acylation

Organic Chemistry

24. Enolate Chemistry: Reactions at the Alpha-Carbon

Enolate Alkylation and Acylation

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5: minutes

Problem 24

Textbook Question

How could you prepare the following compound using a starting material that contains no more than three carbons?

Verified step by step guidance

Step 1: Analyze the target compound. The compound is a ketone with a carbonyl group (C=O) located on the second carbon of a pentane chain. This suggests that the synthesis will involve forming a ketone functional group and constructing the pentane chain.

Step 2: Choose a starting material with no more than three carbons. A suitable starting material could be ethyl bromide (C2H5Br) or propyl bromide (C3H7Br), as these are simple alkyl halides with three or fewer carbons.

Step 3: Perform a Grignard reaction. React ethyl bromide with magnesium in dry ether to form ethylmagnesium bromide (a Grignard reagent). This reagent will be used to extend the carbon chain.

Step 4: React the Grignard reagent with an appropriate carbonyl compound. For example, react ethylmagnesium bromide with propanal (CH3CH2CHO), which contains three carbons, to form a secondary alcohol intermediate. The reaction involves nucleophilic addition of the Grignard reagent to the carbonyl group.

Step 5: Oxidize the secondary alcohol to a ketone. Use an oxidizing agent such as PCC (pyridinium chlorochromate) or Jones reagent to convert the secondary alcohol into the desired ketone, completing the synthesis of the target compound.

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Key Concepts

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

Enolate Formation

Enolates are nucleophilic species formed from the deprotonation of alpha-hydrogens in carbonyl compounds. This process is crucial for reactions such as alkylation and acylation, where the enolate acts as a nucleophile to attack electrophiles. Understanding how to generate enolates from starting materials is essential for synthesizing more complex molecules.

Alkylation Reactions

Alkylation involves the transfer of an alkyl group to a nucleophile, often using enolates derived from carbonyl compounds. This reaction allows for the construction of longer carbon chains from smaller precursors. Mastery of alkylation techniques is vital for building complex organic structures from simple starting materials.

Carbon Chain Length and Reactivity

The reactivity of organic compounds often depends on their carbon chain length and structure. In this context, starting materials with three or fewer carbons can be strategically chosen to ensure that the desired compound can be synthesized through enolate chemistry. Recognizing how to manipulate carbon chain length is key to effective organic synthesis.

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