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

Reducing Agent

Organic Chemistry

13. Alcohols and Carbonyl Compounds

Reducing Agent

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Problem 37

Textbook Question

Show a mechanism for the lithium aluminum hydride reduction of benzoic anhydride.

Verified step by step guidance

Identify the functional groups in benzoic anhydride. It contains two acyl groups (carbonyl groups attached to an oxygen atom).

Recognize that lithium aluminum hydride (LiAlH4) is a strong reducing agent, capable of reducing acyl groups to alcohols.

In the first step of the mechanism, the hydride ion (H-) from LiAlH4 attacks the carbonyl carbon of one of the acyl groups, leading to the formation of a tetrahedral intermediate.

The tetrahedral intermediate collapses, expelling the leaving group (the other acyl group), and forming a benzoate ion.

The benzoate ion is further reduced by another hydride ion from LiAlH4 to form benzyl alcohol. The process is repeated for the second acyl group, resulting in two equivalents of benzyl alcohol after quenching with water (H3O+).

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Key Concepts

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

Lithium Aluminum Hydride (LiAlH4)

Lithium aluminum hydride is a powerful reducing agent commonly used in organic chemistry. It can reduce a variety of functional groups, including carboxylic acids and anhydrides, to their corresponding alcohols. The mechanism involves the transfer of hydride ions (H-) from the LiAlH4 to the electrophilic carbonyl carbon, leading to the formation of an alkoxide intermediate.

Benzoic Anhydride

Benzoic anhydride is a compound formed from two benzoic acid molecules through the removal of water. It contains two carbonyl groups and is reactive towards nucleophiles due to the electrophilic nature of the carbonyl carbons. Understanding its structure and reactivity is crucial for predicting the outcome of its reduction by lithium aluminum hydride.

Reduction Mechanism

The reduction mechanism describes the step-by-step process by which a compound gains electrons or hydrogen, resulting in a decrease in oxidation state. In the case of benzoic anhydride reduction, the mechanism involves nucleophilic attack by the hydride ion on the carbonyl carbon, followed by protonation of the resulting alkoxide to yield the alcohol product. This understanding is essential for illustrating the reaction pathway.