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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4:50 minutes

Problem 24a

Textbook Question

In which step(s) of the hydride reduction of an ester does the compound undergo reduction? (Hint: Count the bonds to oxygen.)

Verified step by step guidance

Step 1: Understand the hydride reduction of an ester. This reaction typically involves the use of a reducing agent like lithium aluminum hydride (LiAlH₄) to convert the ester into an alcohol. The process occurs in multiple steps.

Step 2: Recall the definition of reduction in organic chemistry. Reduction involves a decrease in the number of bonds to oxygen or an increase in the number of bonds to hydrogen in a molecule.

Step 3: Analyze the first step of the reaction. The hydride ion (H⁻) from the reducing agent attacks the carbonyl carbon of the ester, breaking the π bond of the carbonyl group and forming a tetrahedral intermediate. At this stage, the carbonyl carbon gains a bond to hydrogen, which is a reduction step.

Step 4: Examine the second step of the reaction. The tetrahedral intermediate collapses, expelling the leaving group (usually an alkoxide ion, R'O⁻) and forming an aldehyde. This step does not involve a change in the number of bonds to oxygen for the carbonyl carbon, so it is not a reduction step.

Step 5: Consider the final step. The aldehyde undergoes a second hydride attack, forming a new tetrahedral intermediate that eventually becomes a primary alcohol. In this step, the carbonyl carbon again gains a bond to hydrogen, making it another reduction step.

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Key Concepts

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

Hydride Reduction

Hydride reduction is a chemical reaction where a hydride ion (H-) is used to reduce a carbonyl compound, such as an ester, to an alcohol. This process typically involves the transfer of a hydride from a reducing agent, like lithium aluminum hydride (LiAlH4) or sodium borohydride (NaBH4), to the carbonyl carbon, resulting in the formation of an alcohol and the conversion of the carbonyl group.

Ester Structure

Esters are organic compounds characterized by the functional group -COOR, where R is an alkyl or aryl group. In the context of reduction, understanding the structure of esters is crucial, as they contain a carbonyl group (C=O) and an alkoxy group (–O–R). The reduction process involves the conversion of the carbonyl group to an alcohol, which requires counting the bonds to oxygen to determine the extent of reduction.

Bond Counting in Reduction

In organic chemistry, bond counting is a method used to assess the degree of reduction or oxidation of a compound. For esters undergoing hydride reduction, it is essential to count the bonds to oxygen before and after the reaction. The reduction of the carbonyl group (C=O) to an alcohol (C–OH) involves a change from one double bond to one single bond and the addition of a hydrogen atom, indicating a reduction in oxidation state.

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Related Practice

Textbook Question

What amides would you react with LiAlH₄ to form the following amines?

a. benzylmethylamine

b. ethylamine

c. diethylamine

d. triethylamine

Textbook Question

An unknown alcohol with a molecular formula of C₇H₁₄O was oxidized to an aldehyde with HOCl. When an acidic solution of the alcohol was distilled, two alkenes were obtained. The alkene formed in greater yield was determined to be 1-methylcyclohexene. The other alkene formed the original un-known alcohol when treated with BH₃/THF followed by H₂O₂, HO^-, and H₂O. Identify the unknown alcohol.

Textbook Question

Compounds containing deuterium (D = ²H) are useful for kinetic studies and metabolic studies with new pharmaceuticals. One way to introduce deuterium is by using the reagent LiAlD₄, equivalent in reactivity to LiAlH₄. Show how to make these deuterium-labeled compounds, using LiAlD₄ and D₂O as your sources of deuterium, and any non-deuterated starting materials you wish.

(b) CH₃CD₂OH

Textbook Question

When LiAlH₄ reduces 3-methylcyclopentanone, the product mixture contains 60% cis-3-methylcyclopentanol and 40% trans-3-methylcyclopentanol. Use your models, and make three-dimensional drawings to explain this preference for the cis isomer.

Textbook Question

Propose a mechanism for the reduction of octanoyl chloride by lithium aluminum hydride.

Textbook Question

Show how you would synthesize each compound, starting with an ester containing no more than eight carbon atoms. Any other necessary reagents may be used.

(d) Ph₂CHOH

(e) PhCH₂OH

(f) PhCOOH

Textbook Question

Show how you would synthesize the following alcohol by reducing appropriate carbonyl compound.

(d)

Textbook Question

Show how you would synthesize each compound, starting with an ester containing no more than eight carbon atoms. Any other necessary reagents may be used.

(i) HO–(CH₂)₈–OH

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