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

25. Condensation Chemistry

Aldol Condensation

Organic Chemistry

25. Condensation Chemistry

Aldol Condensation

Previous problemNext problem

4:48 minutes

Problem 19b

Textbook Question

Give the expected products for the aldol condensations of (b) phenylacetaldehyde.

Verified step by step guidance

Identify the structure of phenylacetaldehyde. It consists of a benzene ring (phenyl group) attached to a CH2 group, which is further attached to an aldehyde group (-CHO). The molecular formula is C8H8O.

Understand the aldol condensation mechanism. It involves two steps: (1) formation of the enolate ion from the aldehyde or ketone, and (2) nucleophilic attack of the enolate on another molecule of the aldehyde or ketone, followed by dehydration to form an α,β-unsaturated carbonyl compound.

Generate the enolate ion from phenylacetaldehyde. The α-hydrogen (hydrogen on the carbon adjacent to the carbonyl group) is acidic and can be removed by a base to form the enolate ion. Represent this enolate ion as: \( \text{C}_6\text{H}_5\text{CH}=\text{CH}^- \).

Perform the nucleophilic attack. The enolate ion attacks the carbonyl carbon of another molecule of phenylacetaldehyde. This forms a β-hydroxy aldehyde intermediate. Represent this intermediate as: \( \text{C}_6\text{H}_5\text{CH}(\text{OH})\text{CH}(\text{C}_6\text{H}_5)\text{CHO} \).

Dehydrate the β-hydroxy aldehyde intermediate. Under heat or acidic/basic conditions, the intermediate loses a water molecule to form the final α,β-unsaturated carbonyl compound. Represent the product as: \( \text{C}_6\text{H}_5\text{CH}=\text{CH}(\text{C}_6\text{H}_5) \).

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.

Aldol Condensation

Aldol condensation is a reaction between aldehydes or ketones that contain at least one alpha-hydrogen, leading to the formation of beta-hydroxy aldehydes or ketones. This reaction involves the formation of an enolate ion from one carbonyl compound, which then attacks the carbonyl carbon of another, resulting in a beta-hydroxy carbonyl compound. Upon heating, this intermediate can undergo dehydration to yield an α,β-unsaturated carbonyl compound.

Phenylacetaldehyde

Phenylacetaldehyde, also known as 2-phenylethanal, is an aromatic aldehyde with the formula C8H8O. It features a phenyl group attached to an acetaldehyde moiety, which provides it with unique reactivity in aldol condensation reactions. The presence of the aromatic ring influences the stability of the enolate ion formed during the reaction, affecting the overall product distribution.

Enolate Ion

An enolate ion is a resonance-stabilized anion formed from a carbonyl compound when a hydrogen atom is removed from the alpha carbon. This ion plays a crucial role in aldol reactions, as it acts as a nucleophile, attacking the carbonyl carbon of another aldehyde or ketone. The stability of the enolate ion is influenced by the substituents on the carbonyl compound, which can affect the reaction pathway and the final products.

Watch next

Master General Features with a bite sized video explanation from Johnny

Start learning

Related Videos

Related Practice

Textbook Question

Predict the products of aldol condensation, followed by dehydration, of the following ketones and aldehydes.

Textbook Question

Predict the products of aldol condensation, followed by dehydration, of the following ketones and aldehydes.

(b) acetophenone

Textbook Question

Predict the products of aldol condensation, followed by dehydration, of the following ketones and aldehydes.

(a) butyraldehyde

Textbook Question

Give the expected products for the aldol condensations of (c) pentan-3-one.

Textbook Question

Give the expected products for the aldol condensations of (a) propanal.

Textbook Question

The Knoevenagel condensation is a special case of the aldol condensation in which an active methylene compound reacts with an aldehyde or ketone, in the presence of a secondary amine as a basic catalyst, to produce a new C=C. Show the starting materials that made each of these by a Knoevenagel condensation.

(b)

Textbook Question

(c)

Textbook Question

Propose a mechanism for the aldol condensation of cyclohexanone. Do you expect the equilibrium to favor the reactant or the product?

Show more practices

Download the Mobile app

Privacy

Do not sell my personal information

Accessibility

Patent notice

Sitemap