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

Acetal

Organic Chemistry

21. Aldehydes and Ketones: Nucleophilic Addition

Acetal

Previous problemNext problem

1:18 minutes

Problem 36

Textbook Question

Hydration of an aldehyde is also catalyzed by hydroxide ion. Propose a mechanism for the reaction.

Verified step by step guidance

The first step in the mechanism is the nucleophilic attack of the hydroxide ion (OH⁻) on the carbonyl carbon of the aldehyde. This occurs because the carbonyl carbon is electrophilic due to the partial positive charge caused by the electronegativity difference between carbon and oxygen.

As the hydroxide ion attacks the carbonyl carbon, the π-electrons of the C=O bond are pushed onto the oxygen atom, creating a tetrahedral intermediate. This intermediate has a negatively charged oxygen atom (alkoxide ion).

In the next step, the negatively charged oxygen atom (alkoxide) abstracts a proton (H⁺) from water (H₂O), which acts as a proton donor. This step neutralizes the negative charge on the oxygen and forms a geminal diol (a compound with two hydroxyl groups attached to the same carbon).

The reaction is reversible, and the equilibrium between the aldehyde and the geminal diol is influenced by the stability of the aldehyde and the reaction conditions (e.g., pH, solvent).

The hydroxide ion acts as a catalyst in this reaction, as it is regenerated at the end of the mechanism. This means that the hydroxide ion facilitates the reaction without being consumed in the process.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

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

Aldehyde Structure and Reactivity

Aldehydes are organic compounds characterized by the presence of a carbonyl group (C=O) at the end of a carbon chain. This structure makes them highly reactive, particularly in nucleophilic addition reactions. Understanding the electrophilic nature of the carbonyl carbon is crucial, as it is susceptible to attack by nucleophiles, such as water in hydration reactions.

Nucleophilic Addition Mechanism

The nucleophilic addition mechanism involves the attack of a nucleophile on the electrophilic carbon of a carbonyl group. In the case of aldehydes, hydroxide ions (OH-) can act as nucleophiles, leading to the formation of a tetrahedral intermediate. This intermediate can then undergo protonation to yield the corresponding alcohol, illustrating the transformation of the aldehyde into a hydrated form.

Role of Hydroxide Ion as a Catalyst

Hydroxide ions can catalyze the hydration of aldehydes by facilitating the nucleophilic attack on the carbonyl carbon. As a base, OH- can enhance the reactivity of water, allowing for a more efficient formation of the tetrahedral intermediate. This catalytic role is essential in organic reactions, as it lowers the activation energy and increases the reaction rate without being consumed in the process.

Watch next

Master General Mechanism with a bite sized video explanation from Johnny

Start learning

Related Videos

Related Practice

Textbook Question

For each compound,

1. name the functional group.

2. show what compound(s) result from complete hydrolysis.

(e)

Textbook Question

There are three dioxane isomers: 1,2-dioxane, 1,3-dioxane, and 1,4-dioxane. One of these acts like an ether and is an excellent solvent for Grignard reactions. Another one is potentially explosive when heated. The third one quickly hydrolyzes in dilute acid. Show which isomer acts like a simple ether, and then explain why one of them is potentially explosive.

Textbook Question

There are three dioxane isomers: 1,2-dioxane, 1,3-dioxane, and 1,4-dioxane. One of these acts like an ether and is an excellent solvent for Grignard reactions. Another one is potentially explosive when heated. The third one quickly hydrolyzes in dilute acid. Propose a mechanism for the acid hydrolysis of the third isomer.

Textbook Question

Simple aminoacetals hydrolyze quickly and easily in dilute acid. Propose a mechanism for hydrolysis of the following aminoacetal:

Textbook Question

Which of the following are a. hemiacetals? b. acetals? c. hydrates?

Textbook Question

Which of the following are a. hemiacetals? b. acetals? c. hydrates?

Textbook Question

Identify A through O:

Textbook Question

In Section 17.7.4, we studied the acid-catalyzed hydrolysis of acetals. The acetal shown here resists hydrolysis by the mechanism in Figure 17.63. Why? [Draw the intermediates as if the reaction would occur, then analyze the intermediates for any problems.]

Show more practices

Download the Mobile app

Privacy

Do not sell my personal information

Accessibility

Patent notice

Sitemap