Enolate Ion Formation and Alpha Acidity
Start with the big picture
An α-hydrogen is attached to the carbon next to a carbonyl. Removing it can produce an enolate, whose negative charge is represented at either carbon or oxygen through resonance. The carbonyl group contributes to α-hydrogen acidity through resonance stabilization of the enolate and inductive electron withdrawal. The source compares approximate acidity across carbonyl compounds, highlighting the greater acidity of 1,3-dicarbonyl compounds. It also introduces how base strength, temperature, and reversibility affect enolate formation, including the distinction between kinetic and thermodynamic enolates. Enolate chemistry links to reactions such as aldol and Claisen condensations, while enamines offer a neutral enolate equivalent. Together, these concepts help explain how α-position reactivity can be generated and controlled.
What you'll learn
- Define an α-hydrogen and explain the factors contributing to its acidity.
- Describe the resonance forms and carbon- and oxygen-centered reactivity of an enolate.
- Compare the relative α-hydrogen acidity of the carbonyl compounds presented.
- Distinguish kinetic from thermodynamic enolate formation by conditions and substitution.
- Recognize how enolate formation initiates major carbonyl reactions.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
