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

13. Alcohols and Carbonyl Compounds

Organometallic Cumulative Practice

Organic Chemistry

13. Alcohols and Carbonyl Compounds

Organometallic Cumulative Practice

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5:15 minutes

Problem 13b

Textbook Question

Show how you might synthesize the following compounds starting with bromobenzene, and alkyl or alkenyl halides of four carbon atoms or fewer.
b. 5-methylhex-2-ene

Verified step by step guidance

Step 1: Begin with bromobenzene as the starting material. Perform a Friedel-Crafts alkylation reaction using a suitable alkyl halide (e.g., 1-bromopropane) and a Lewis acid catalyst such as AlCl₃. This will introduce a propyl group onto the benzene ring, forming propylbenzene.

Step 2: Perform a benzylic bromination on the propylbenzene using N-bromosuccinimide (NBS) and light (hv) to selectively brominate the benzylic position, forming 1-bromo-3-phenylpropane.

Step 3: Carry out a Wurtz reaction by reacting 1-bromo-3-phenylpropane with an alkyl halide (e.g., methyl iodide) in the presence of sodium metal. This will couple the two alkyl chains, forming 5-phenylhexane.

Step 4: Perform a dehydrohalogenation reaction to introduce a double bond. Use a strong base such as potassium tert-butoxide (t-BuOK) to eliminate a hydrogen and a halogen, forming 5-phenylhex-2-ene.

Step 5: Finally, perform a hydrogenation reaction using a catalyst such as Pd/C and hydrogen gas (H₂) to selectively remove the phenyl group, leaving behind 5-methylhex-2-ene as the desired product.

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Key Concepts

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

Electrophilic Aromatic Substitution

Electrophilic aromatic substitution (EAS) is a fundamental reaction in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. In the case of bromobenzene, the bromine atom can be replaced by various electrophiles, allowing for the introduction of different substituents. Understanding EAS is crucial for synthesizing compounds from aromatic starting materials.

Alkylation Reactions

Alkylation reactions involve the introduction of an alkyl group into a molecule, often through nucleophilic substitution or EAS. When synthesizing 5-methylhex-2-ene, alkyl halides can be used to add carbon chains to the aromatic ring or to create branched alkenes. Mastery of alkylation techniques is essential for constructing complex organic molecules.

Elimination Reactions

Elimination reactions are processes where two atoms or groups are removed from a molecule, resulting in the formation of a double bond. In the synthesis of 5-methylhex-2-ene, elimination reactions can be employed to convert alkyl halides into alkenes. Understanding the mechanisms and conditions for elimination is vital for achieving the desired product in organic synthesis.

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Textbook Question

For each synthesis, start with bromocyclohexane and predict the products. Assume that an excess of each reactant is added so that all possible reactions that can happen will happen.

(a)