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

Oxidizing Agent

Organic Chemistry

13. Alcohols and Carbonyl Compounds

Oxidizing Agent

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Problem 21

Textbook Question

In light of Figure 24.22, provide a mechanism by which para-dihydroxybenzene is oxidized to para-quinone.

Verified step by step guidance

Identify the starting material as para-dihydroxybenzene, which has two hydroxyl groups attached to a benzene ring in the para position.

Recognize the oxidizing agent as chromic acid (H₂CrO₄), which is commonly used to oxidize alcohols to carbonyl compounds.

Understand that the mechanism involves the oxidation of the hydroxyl groups to carbonyl groups, forming para-quinone.

Propose that the first step involves the formation of a chromate ester intermediate, where the hydroxyl oxygen attacks the chromium atom, forming a bond and releasing water.

Suggest that the chromate ester undergoes a two-electron oxidation, where the C-O bond is cleaved, forming a carbonyl group and reducing the chromium species, resulting in the formation of para-quinone.

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Key Concepts

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

Oxidation-Reduction Reactions

Oxidation-reduction (redox) reactions involve the transfer of electrons between species, leading to changes in oxidation states. In the context of organic chemistry, oxidation often refers to the loss of hydrogen or the gain of oxygen, while reduction is the opposite. Understanding these processes is crucial for analyzing how para-dihydroxybenzene can be converted to para-quinone through the removal of electrons and protons.

Mechanism of Electrophilic Aromatic Substitution

Electrophilic aromatic substitution (EAS) is a fundamental reaction mechanism in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. In the case of para-dihydroxybenzene, the hydroxyl groups can activate the ring towards electrophilic attack, facilitating the formation of para-quinone. Recognizing the role of substituents in directing the reaction is essential for understanding the mechanism involved.

Resonance and Stability of Intermediates

Resonance refers to the delocalization of electrons within a molecule, which can stabilize reaction intermediates. In the oxidation of para-dihydroxybenzene, the formation of a resonance-stabilized carbocation intermediate is key to the reaction pathway. Understanding how resonance affects the stability of intermediates helps predict the feasibility and outcome of the oxidation process leading to para-quinone.

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Related Practice

Textbook Question

Predict the product(s) that would result when molecules (a)–(p) are allowed to react under the following conditions: (xi) HOCl, H₂O (xii) HIO₄. If no reaction occurs, write 'no reaction.'

(a)

Textbook Question

We explain in Chapter 24 that bisphenols can be oxidized to quinones.

(a) Calculate the oxidation numbers of C1 and C₂ in going from reactant to product.

(b) Provide a mechanism for this transformation. [The reaction begins like the alcohol oxidations of Section 13.9.]

Textbook Question

In Assessment 13.48, identify the individual step that represents the general mechanism for all alcohol oxidation reactions.

Textbook Question

Predict the product(s) that would result when molecules (a)–(p) are allowed to react under the following conditions: (i) SOCl₂ ; (ii) PBr₃ ; (iii) SOCl₂ , NEt₃ (iv) 1. TsCl, Et₃N 2. NaCN; (v) 1. TsCl, Et₃N 2. NaOt-Bu (vi) H₂SO₄ (vii) HCl; (viii) HBr; (ix) PCC; (x) H₂CrO₄ , H₂O (xi) HOCl, H₂O (xii) HIO₄ If no reaction occurs, write 'no reaction.'

(c)

Textbook Question

Assessment 24.22 asked why meta-dihydroxybenzene could not be oxidized to meta-quinone. The attempted oxidation instead gives rise to three different quinone products. Suggest a mechanism for the formation of each.

Textbook Question

Draw a mechanism for the following oxidation reactions.

(d)

Textbook Question

Draw a mechanism for the following oxidation reactions.

(c)

Textbook Question

Predict the product(s) that would result when molecules (a)–(p) are allowed to react under the following conditions: (ix) PCC; (x) H₂CrO₄ , H₂O. If no reaction occurs, write 'no reaction.'

(o)

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