WWU -- Chemistry Reactions of  Hydrogens: Condensation Reactions Chapter 21 These images should be printed in color, if possible, otherwise the images are very faint! It would be better to look at them on a computer monitor.

WWU -- Chemistry Assignments for Chapter 21 and 22 Chapter 20, hardly any, attend class! Skip these sections from Chap , 21.6, 21.8, 21.11, and Skip these sections from Chap , 22.4, through Keep and 22.17!!!

WWU -- Chemistry Problems for Chapter 21 In-Text Problems: –2, 3, 4, 8, 13, 14, 18, 19, 26, 29, 30, 32, 34, 35, 36, 37, 40, 46 and 50 End-of-Chapter Problems: –2, 4, 5, 9, 13, 16, 17 and 21

WWU -- Chemistry Sect. 21.1: Keto-Enol Tautomerism

WWU -- Chemistry Keto-Enol Tautomerism in 1,3- Dicarbonyl Compounds

WWU -- Chemistry Keto-Enol Tautomerism in 1,3- Dicarbonyl Compounds The equilibrium lies substantially to the right with 1,3-dicarbonyl compounds. In simple ketones, such a hydrogen-bonded structure cannot form, and the percentage of enol found in an equilibrium mixture is very small (equilibrium lies to left).

WWU -- Chemistry Some Representative Enol Percents

WWU -- Chemistry Sect Acidity of  - Hydrogens The acidity of a hydrogen attached to the  -carbon of a carbonyl compound is much higher than the acidity of a typical C-H hydrogen. pK a values range from about 19 to 20 (compared with 48 to 50) for alkanes.

WWU -- Chemistry Acidity of  -Hydrogens: The Reason

WWU -- Chemistry Acidity of  -Hydrogens Resonance stabilization of the enolate ion shifts the equilibrium to the right, thereby making the C-H bond more acidic. Once formed, the enolate ion is capable of reacting as a nucleophile. The  - carbon of the enolate ion bears substantial negative charge.

WWU -- Chemistry Sect Halogenation of Ketones

WWU -- Chemistry Mechanism

Example

But... The halogenation is difficult to stop at the mono-substitution stage. Often, poly-halogenated products are formed in this reaction.

WWU -- Chemistry With an excess of bromine:

WWU -- Chemistry In base, bromoform is formed

WWU -- Chemistry Section 21.5: Iodoform reaction

WWU -- Chemistry Sect. 21.7: Alkylation Reactions

WWU -- Chemistry Example

Sect. 21.9: Alkylation of Active Methylene Compounds

WWU -- Chemistry Sect: 21.10: Hydrolysis and decarboxylation

WWU -- Chemistry Mechanism of decarboxylation

WWU -- Chemistry Alkylation of ethyl acetoacetate

WWU -- Chemistry Sect : Decarboxylation

WWU -- Chemistry Sect : The Aldol Condensation

WWU -- Chemistry Aldol Condensation -- Mechanism

WWU -- Chemistry An example

WWU -- Chemistry One More:

WWU -- Chemistry Synthesis Problem

WWU -- Chemistry Sect : Dehydration of Aldol products Aldol products easily dehydrate in acid and sometimes in base.

WWU -- Chemistry Dehydration of Aldol Products

WWU -- Chemistry Dehydration of Aldol Products Note here that iodine is a sufficiently strong Lewis acid to bring about dehydration.

WWU -- Chemistry Also:

Synthesis of:

WWU -- Chemistry Synthesis of a Compound used in Perfumery

WWU -- Chemistry Preparation via Aldol Condensation and reduction

WWU -- Chemistry Preparation via Aldol Condensation and reduction!

WWU -- Chemistry Synthesis of an Insect Repellent

WWU -- Chemistry Sect : Crossed Aldol Condensations Reaction of two different aldehydes: One with an " -hydrogen (donor) Other with no " -hydrogen (acceptor)

WWU -- Chemistry Crossed Aldol Condensations acceptor donor

WWU -- Chemistry Chalcone formation: part 1

WWU -- Chemistry Chalcone Formation: part 2 (formed from an aldol condensation)

WWU -- Chemistry Do the synthesis of:

WWU -- Chemistry Sect : The Claisen Ester Condensation

WWU -- Chemistry Claisen Ester Condensation -- Mechanism (Part One)

WWU -- Chemistry Claisen Ester Condensation -- Mechanism (Part Two)

WWU -- Chemistry Example

Another Example

WWU -- Chemistry Example of a Ring Formation This reaction is known as the Dieckmann cyclization.

WWU -- Chemistry Sect : Crossed Claisen Condensation In the crossed Claisen condensation, we choose one of the esters to be the acceptor. The acceptor does not have  -hydrogens. The other ester, the donor, does have  - hydrogens. It can react with base to form a nucleophilic enolate ion. With such an experimental design, the crossed Claisen condensation can be used successfully.

WWU -- Chemistry Crossed Claisen Condensation -- An Example

WWU -- Chemistry Synthesize this:

WWU -- Chemistry Sect : 1,2 vs. 1,4-addition

WWU -- Chemistry Sect : Conjugate addition: Michael reaction

WWU -- Chemistry Sect : copper catalyzed conjugate addition reactions