Ch. 21 - Enolate Chemistry: Reactions at the Alpha-Carbon WorksheetSee 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

Concept #1: Unusual Acidity of the Alpha Carbon

Concept #2: Tautomerization Mechanisms

Practice: Draw the enol tautomer for cyclopentanone

Additional Problems
How many α-hydrogens does 2-hexanone have? a 1 b 2 c 3 d 4 e 5  
Which of the following is not correct? a Tautomerization is catalyzed by both acids and bases. b Tautomers are constitutional isomers. c Tautomers rapidly interconvert. d The enol form is generally more stable. e All of the above are correct with respect to tautomers.
Draw the enol tautomer for the following ketone:
Write out the mechanism for the following transformation.
Write out the mechanism for the following transformation.
How many acidic protons (pKa ≤ 20) are in the following compound?
Consider each of the equilibria shown below. Does the equilibrium lie to the left or to the right?
How many tautomers can you draw? 
Identify the keto form of the following enol. a 1-penten-3-one b (E)-3-penten-2-one c 2-pentanone d (E)-3-pentenal e (Z)-3-penten-2-one
Consider the structural formula of acetaldehyde below. (a) Give a chemical equation for the reaction between hydroxide ion (HO -) and acetaldehyde in which HO- acts as a Lewis base and acetaldehyde acts as a Lewis acid. IMPORTANT: The Lewis base that you give cannot be a Bronsted-Lowry base; the Lewis acid that you give cannot be a Bronsted-Lowry acid. Note: Use Lewis structures for each reactant/product and use curved arrows appropriately.            (b) Using Lewis structures for each reactant and each product and using curved arrows appropriately to show the flow of electrons in the reactants, give a chemical equation for the reaction between hydroxide ion (HO -) and acetaldehyde in which HO- acts as a Bronsted-Lowry base and acetaldehyde acts as a Bronsted-Lowry acid. Do not give the same answer that you gave in the first part of this question.           
Estimate Keq for the following reaction and explain if the equilibrium favors the reactants or the products. pKa α-H cyclohexanone 20; pKa HCN 9; pKa β-H cyclohexanone 40 
The following reaction process is an example of A. Resonance B. Conjugation C. Oxidation D. Acetalization E. Tautomerism
Which represents a keto-enol tautomerization?
Refer to the reaction drawn below to answer the following questions.   In the presence of acid or a base a ketone can be converted into an ___________. This process is called _______________________. The ketone predominates because _______________________________________________________.  
Which of the following is (are) a keto-enol tautomeric pair(s)?
Which of the following is a keto-enol tautomeric pair?
The final step in the hydration of an alkyne under both acidic and basic conditions is the tautomerization of an enol intermediate to give the corresponding carbonyl. Provide an arrow-pushing mechanism for the tautomerization under acidic conditions. 
Provide a mechanism for the following reaction. Be sure to include all intermediates, formal charges and arrows depicting electron movement.
Draw the enol tautomers of the following ketone
Addition of water to an alkyne gives a keto-enol tautomer product. Draw the ketone that is in equilibrium with the given enol.  
Draw the enol that is in equilibrium with the given aldehyde.
Draw the structural formula of the enol tautomer of cyclopentanone. 
Carbonyl Compounds: Draw the keto tautomer of cyclohexenol. 
Draw the keto tautomeric form of the following compound: 
Carbonyl Compounds: Draw the ketotautomer of (2z)-but-2-en-2ol
Draw the keto and enol forms of propanone.