Aldehydes, ketones
Required background: Structure of alkenes Nucleophilic substitution S N 1, S N 2 Essential for: 1. Carboxylic aids and their derivatives, lipids 2. Enols, enolates 3. Aminoacids, peptides 4. Carbohydrates and nucleic acids
Outline 1. Structure and physical properties of carbonyl compounds 2. Nomenclature of aldehydes and ketones 3. Preparation of aldehydes and ketones 4. Nucleophilic addition to the carbonyl group 5. Reduction of aldehydes and ketones 7. Acetals and their use in synthesis 8. Reaction of aldehydes and ketones with ammonia and primary amines 9. Enoles and enolates 10. Aldol condensation
Outline 1. Structure and physical properties of carbonyl compounds 2. Nomenclature of aldehydes and ketones 3. Preparation of aldehydes and ketones 4. Nucleophilic addition to the carbonyl group 5. Reduction of aldehydes and ketones 7. Acetals and their use in synthesis 8. Reaction of aldehydes and ketones with ammonia and primary amines 9. Enoles and enolates 10. Aldol condensation
Outline 1. Structure and physical properties of carbonyl compounds 2. Nomenclature of aldehydes and ketones 3. Preparation of aldehydes and ketones 4. Nucleophilic addition to the carbonyl group 5. Reduction of aldehydes and ketones 7. Acetals and their use in synthesis 8. Reaction of aldehydes and ketones with ammonia and primary amines 9. Enoles and enolates 10. Aldol condensation
Preparation of aldehydes and ketones a. Oxidation of alcohols b. Friedel-Crafts acylation c. Hydration of alkynes d. Ozonolysis of alkenes e. Cleavage of glycols Nucleophilic addition to the carbonyl group
Aldehydes are more reactive, than ketones due to the steric reasons and a larger positive charge on the carbonyl carbon in aldehydes. Addition to C=O bonds is faster, than addition to C=C bonds due to the higher polarity of the C=O bond, but less favorable thermodynamically due to the stronger C=O bond vs. the C=C bond. Example: Cyanohydrin synthesis Reduction of aldehydes and ketones
Outline 1. Structure and physical properties of carbonyl compounds 2. Nomenclature of aldehydes and ketones 3. Preparation of aldehydes and ketones 4. Nucleophilic addition to the carbonyl group 5. Reduction of aldehydes and ketones 7. Acetals and their use in synthesis 8. Reaction of aldehydes and ketones with ammonia and primary amines 9. Enoles and enolates 10. Aldol condensation
Examples:
Acetals and hemiacetals can be formed intramolecularly Due to the stability of acetals toward bases and nucleophiles, they are often used as protecting groups
Outline 1. Structure and physical properties of carbonyl compounds 2. Nomenclature of aldehydes and ketones 3. Preparation of aldehydes and ketones 4. Nucleophilic addition to the carbonyl group 5. Reduction of aldehydes and ketones 7. Acetals and their use in synthesis 8. Reaction of aldehydes and ketones with ammonia and primary amines 9. Enoles and enolates 10. Aldol condensation
Reactions of aldehydes and ketones with ammonia and its derivatives
Examples:
Outline 1. Structure and physical properties of carbonyl compounds 2. Nomenclature of aldehydes and ketones 3. Preparation of aldehydes and ketones 4. Nucleophilic addition to the carbonyl group 5. Reduction of aldehydes and ketones 7. Acetals and their use in synthesis 8. Reaction of aldehydes and ketones with ammonia and primary amines 9. Enoles and enolates 10. Aldol condensation
The equilibrium is strongly shifted toward the carbonyl form, especially in polar solvents
In esters, enolization is even less favorable due to stabilization of the carbonyl group. Stabilization of the carbonyl form decreases acidity of the compound
Stabilization of the double bond (by conjugation) shifts the equilibrium toward the enol. Enolization, catalyzed by acids
Outline 1. Structure and physical properties of carbonyl compounds 2. Nomenclature of aldehydes and ketones 3. Preparation of aldehydes and ketones 4. Nucleophilic addition to the carbonyl group 5. Reduction of aldehydes and ketones 7. Acetals and their use in synthesis 8. Reaction of aldehydes and ketones with ammonia and primary amines 9. Enoles and enolates 10. Aldol condensation
Aldol reaction (acid catalyzed)
Aldol reaction (base catalyzed)
Examples: