Ch. 22 - Condensation ChemistrySee all chapters
All Chapters
Ch. 1 - A Review of General Chemistry
Ch. 2 - Molecular Representations
Ch. 3 - Acids and Bases
Ch. 4 - Alkanes and Cycloalkanes
Ch. 5 - Chirality
Ch. 6 - Thermodynamics and Kinetics
Ch. 7 - Substitution Reactions
Ch. 8 - Elimination Reactions
Ch. 9 - Alkenes and Alkynes
Ch. 10 - Addition Reactions
Ch. 11 - Radical Reactions
Ch. 12 - Alcohols, Ethers, Epoxides and Thiols
Ch. 13 - Alcohols and Carbonyl Compounds
Ch. 14 - Synthetic Techniques
Ch. 15 - Analytical Techniques: IR, NMR, Mass Spect
Ch. 16 - Conjugated Systems
Ch. 17 - Aromaticity
Ch. 18 - Reactions of Aromatics: EAS and Beyond
Ch. 19 - Aldehydes and Ketones: Nucleophilic Addition
Ch. 20 - Carboxylic Acid Derivatives: NAS
Ch. 21 - Enolate Chemistry: Reactions at the Alpha-Carbon
Ch. 22 - Condensation Chemistry
Ch. 23 - Amines
Ch. 24 - Carbohydrates
Ch. 25 - Phenols
Ch. 26 - Amino Acids, Peptides, and Proteins

An aldol reaction gets its name from the 2 functional groups that make it up. Let's take a look at how we can distinguish this condensation from others. 

Concept #1: General Features

Practice: What product can be isolated from the following aldol condensation reaction? 

Practice: Provide the mechanism for the following transformation.

Additional Problems
Draw the structures of the dehydration products expected if the aldol reactions below are exposed to strong acidic conditions.
Give the structure of the hydroxyaldehyde product of the aldol condensation (at 5°C) of 2-phenylacetaldehyde.
Which of the following are intermediates in the acid catalyzed aldol reaction of propanal to form 2-methyl-2-pentenal? 1. enol 2. enolate 3. tetrahedral carbonyl intermediate 4. aldol a only 1 and 2  b only 1, 3 and 4  c only 2, 3 and 4  d 1, 2, 3 and 4  e 1, 2 and 3
Which of the following statements describes the first step in the mechanism of the aldol condensation? a An α hydrogen is abstracted by the base to form an enolate anion. b A nucleophilic base attacks the carbonyl carbon atom. c The carbonyl oxygen is protonated by the base ion. d The α hydrogen is abstracted by an acid to the enolate anion. e The carbonyl oxygen of one aldehyde attacks the carbonyl carbon of another.  
This reaction is an example of: A) Claisen Condensation Reaction B) Aldol Condensation Reaction C) Dieckmann Condensation Reaction D) Conjugate Reduction Reaction E) None of the Above
When 2-butanone is heated in the presence of aqueous sodium hydroxide, two constitutionally isomeric condensation products are obtained. Draw both products. 
Propose a synthesis of the compound shown, from the starting material(s) specified and any other needed reagents or solvents.   
Which compound is the product of an aldol condensation?
An aldol reaction can produce an addition product or the dehydrated addition product (condensation product). What factor favors the formation of the dehydration product?
Which is not true of the aldol reaction? A) It accomplishes the formation of a new carbon-carbon bond. B) The key step in the mechanism is attack of the α-carbon atom of an enolate ion on a carbonyl carbon atom. C) Dehydration of the aldol product is often observed (an aldol condensation). D) The enolate is favored at equilibrium.  
What would be the major product of this reaction?
Which of these is not a step in the mechanism of the aldol reaction?
Which of these compounds cannot undergo an aldol reaction in the presence of dilute base?
The first two steps in the base-catalyzed condensation of acetaldehyde would be described as  A) attack of  –OH on the carbonyl carbon atom, then loss of water.  B) attack of  –OH on the carbonyl carbon atom, then the resultant anion attacks the carbonyl atom on a second molecule of acetaldehyde. C) –OH abstracts an α-hydrogen, then the resultant anion attacks the carbonyl carbon atom on a second molecule acetaldehyde. D) –OH abstracts the hydrogen atom from the carbonyl atom, then the resultant anion attacks the carbonyl carbon atom on a second molecule of acetaldehyde. 
Aldol condensations, even with ketones, can occur under acid conditions where the active nucleophile is the enol, not the enolate ion. For the aldol condensation shown for acetone, what would be the structure of the electrophilic species that the enol attacks?
Complete the following reaction by drawing the structure of the principal major product. Indicate relative stereochemistry where necessary. If there is no reaction, write NR.
Provide the missing reagents and draw the mechanism to complete this transformation.
What is the product of the following reaction?
Theoretically, what is the maximum number of b-hydroxy aldehyde stereoisomers that could be formed in the self-aldol reaction of propanaldehyde? Show them.
Show all stereoisomeric b-hydroxyaldehyde that could from the self-aldol condensation of isobutylaldehyde.
Give the major product for the following condensation reaction.
Predict the major product for the following reaction.