Chapter 23 CHEM 140B

Chapter 23 CHEM 140B - Chapter 23: Ester Enolates and The...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
I. Properties & Reactivity A. β-dicarbonyls are compounds with two carbonyls separated by an α-carbon B. Hydrogens on the α-carbons are very acidic because of the resonance stabilization by both carbonyls II. Claisen Condensation A. β-dicarbonyls can be made by the formation of ester enolate followed by addition-elimination of another ester. B. Step 1: Ester enolate formation B.1.Not favorable due to the big differences in pKa’s between ethanol and reactant. Very little of the ester enolate will be present but it will be enough to proceed C. Step 2: Nucleophilic addition D. Step 3: Elimination D.1.Although alkoxide is a relatively strong base and is not a good leaving group in Sn2 reactions, it is an ok leaving group in an elimination reactant under strongly basic conditions E. Step 4: Deprotonation of ketoester drives equlibirum E.1. Steps 1-3 are reversible (equilibrium constants are not all that favorable). Deprotonation of the second H is a strongly favored acid-base reaction and serves to drive the reaction to its endpoint. F.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/27/2012 for the course CHEM 140B CHEM 140B taught by Professor Theodorakis during the Spring '10 term at UCSD.

Page1 / 6

Chapter 23 CHEM 140B - Chapter 23: Ester Enolates and The...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online