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

21. Aldehydes and Ketones: Nucleophilic Addition

DIBAL

Organic Chemistry

21. Aldehydes and Ketones: Nucleophilic Addition

DIBAL

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4:41 minutes

Problem 39c

Textbook Question

Predict the major products of the following reactions.
(c)

Verified step by step guidance

Step 1: Identify the functional group in the starting material. The molecule contains a terminal alkyne group (-C≡CH). This functional group is reactive under the conditions provided.

Step 2: Recognize the reagent and its role. DIBAL-H (Diisobutylaluminum hydride) is a reducing agent that selectively reduces certain functional groups, such as esters, nitriles, and alkynes, under controlled conditions (e.g., -78°C). It is often used to stop the reduction at an intermediate stage.

Step 3: Predict the intermediate formed after the first step. DIBAL-H at low temperatures (-78°C) reduces the alkyne group to an aldehyde. This occurs because DIBAL-H selectively adds hydrogen to the triple bond, forming a double bond and introducing an oxygen atom.

Step 4: Consider the second step of the reaction. The addition of water (H₂O) in the second step is used to hydrolyze the aluminum complex formed during the reduction, yielding the final product.

Step 5: Combine the information to predict the major product. The major product of this reaction will be an aldehyde derived from the reduction of the terminal alkyne group. The cyclic structure remains intact, and the aldehyde group (-CHO) will be attached to the carbon that was part of the triple bond.

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Key Concepts

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

DIBAL-H (Diisobutylaluminum Hydride)

DIBAL-H is a strong reducing agent commonly used in organic chemistry to selectively reduce esters and nitriles to aldehydes. At low temperatures, such as -78°C, it allows for controlled reduction, preventing over-reduction to alcohols. Understanding its reactivity and selectivity is crucial for predicting the products of reactions involving carbonyl compounds.

Aldehyde Formation

The reaction of DIBAL-H with an ester or nitrile typically results in the formation of an aldehyde. This occurs because DIBAL-H adds to the carbonyl carbon, leading to the formation of an intermediate that can be hydrolyzed upon the addition of water. Recognizing the mechanism of aldehyde formation is essential for predicting the major products in the given reaction.

Hydrolysis

Hydrolysis is the chemical process in which water reacts with a compound, leading to the breakdown of that compound. In the context of the reaction with DIBAL-H, the addition of water after the reduction step converts the intermediate formed into the final aldehyde product. Understanding hydrolysis is important for determining the final outcome of the reaction sequence.

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