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

19. Reactions of Aromatics: EAS and Beyond

EAS:Retrosynthesis

Organic Chemistry

19. Reactions of Aromatics: EAS and Beyond

EAS:Retrosynthesis

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2:56 minutes

Problem 76

Textbook Question

The antioxidants BHA and BHT are commonly used as food preservatives. Show how BHA and BHT can be made from phenol and hydroquinone

Verified step by step guidance

Step 1: Begin with phenol (C₆H₅OH) and hydroquinone (C₆H₄(OH)₂) as the starting materials. Phenol has one hydroxyl group attached to a benzene ring, while hydroquinone has two hydroxyl groups attached to a benzene ring in a para configuration.

Step 2: To synthesize BHA (butylated hydroxyanisole), perform an alkylation reaction on phenol. Use tert-butyl chloride (C(CH₃)₃Cl) as the alkylating agent and a Lewis acid catalyst such as AlCl₃ to introduce the tert-butyl group at the para position relative to the hydroxyl group. Then, methylate the hydroxyl group using dimethyl sulfate or methyl iodide to form the methoxy group (-OCH₃).

Step 3: To synthesize BHT (butylated hydroxytoluene), start with hydroquinone. Perform an alkylation reaction using tert-butyl chloride (C(CH₃)₃Cl) and a Lewis acid catalyst (e.g., AlCl₃) to introduce tert-butyl groups at the ortho and para positions relative to one of the hydroxyl groups. Then, methylate one hydroxyl group using dimethyl sulfate or methyl iodide to form the methyl group (-CH₃).

Step 4: Ensure regioselectivity during the alkylation reactions by controlling the reaction conditions and using appropriate catalysts. The tert-butyl groups are introduced at specific positions due to the electronic and steric effects of the hydroxyl groups.

Step 5: Purify the products (BHA and BHT) using techniques such as recrystallization or chromatography to remove any unreacted starting materials or side products. Confirm the structures using spectroscopic methods like NMR or IR.

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Key Concepts

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

Phenol and Hydroquinone

Phenol is a simple aromatic compound with a hydroxyl group (-OH) attached to a benzene ring, while hydroquinone has two hydroxyl groups on the benzene ring. Both compounds serve as precursors in organic synthesis, particularly in the formation of antioxidants like BHA and BHT. Understanding their structures and reactivity is crucial for manipulating them in chemical reactions.

Antioxidants

Antioxidants are substances that inhibit oxidation, a chemical reaction that can produce free radicals leading to chain reactions that may damage cells. BHA (Butylated Hydroxyanisole) and BHT (Butylated Hydroxytoluene) are synthetic antioxidants derived from phenolic compounds, widely used in food preservation to prevent rancidity and extend shelf life. Their mechanism involves donating electrons to free radicals, stabilizing them.

Synthetic Pathways

Synthetic pathways refer to the series of chemical reactions that transform starting materials into desired products. In the case of BHA and BHT, these pathways involve alkylation and methylation reactions of phenol and hydroquinone. Understanding these synthetic routes is essential for predicting the formation of these antioxidants and optimizing their production in a laboratory or industrial setting.

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