CHEM 140B Chapter 18: Textbook Notes
15 Mar 2017
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Ochem textbook notes chapter 18: enols, enolates, and the aldol condensation. 18. 1 acidity of aldehydes and ketones: enolate ions. Pka of aldehyde and ketone alpha hydrogens: 16-21: strong bases can remove alpha-hydrogens, can use lithium diisopropylamide (lda) to form enolates. Enol and keto tautomerism: enols rapidly interconvert between enols and ketones: keto form usually predominates. Aldehydes and ketones react with halogens at the alpha carbon. Extent of halogenation depends on whether acid or base catalysis has been used. Halogenation in presence of acid: usually stops after the first halogen is introduced, rate is independent of halogen concentration, mechanism: further haloge(cid:374)atio(cid:374) does(cid:374)"t happe(cid:374) since you would need to enolize the carbonyl again. 18. 5 attack by enolates on the carbonyl function: aldol condensation. Aldehydes undergo base-catalyzed condensations: convert aldehyde to an aldol (aldehyde alcohol, convert aldol into an unsaturated aldehyde. 18. 8 properties of alpha, beta-unsaturated aldehydes and ketones.
