Chapter_18_Enols,_Enolates,_Aldol_(Lectures_11_&_12)

Chapter_18_Enols,_Enolates,_Aldol_(Lectures_11_&_12)...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 18 – Enols, Enolates, Aldol Instructor: Dr. Daniel Seidel The pK a values of the α -hydrogens of aldehydes and ketones range from 16 to 21, comparable to those of alcohols (15-18). Strong bases can remove α hydrogens leading to anions called enolate ions or enolates . O LDA OLi N H + + Li Butylithium cannot be used to deprotonate aldehydes and ketones. Why? A Li-enolate
Background image of page 1

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

View Full DocumentRight Arrow Icon
Keto-Enol Equilibria Base catalysis: Acid catalysis:
Background image of page 2
Keto-Enol Equilibria For ordinary aldehydes and ketones, only traces of the enol form are present. The enol form is less stable by 8-12 kcal mol -1 . However for acetaldehyde, the enol form is about 100 times more stable than that of acetone because the less substituted aldehyde carbonyl is more stable than the more substituted ketone carbonyl.
Background image of page 3

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

View Full DocumentRight Arrow Icon
Enolates as Ambident Nucleophiles
Background image of page 4
Hydrogen-Deuterium Exchange of Enolizable Hydrogens Mechanism:
Background image of page 5

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

View Full DocumentRight Arrow Icon
Background image of page 6
Acid Catalyzed Halogenation of Aldehydes and Ketones Mechanism:
Background image of page 7

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

View Full DocumentRight Arrow Icon
Base Catalyzed Halogenation: The Haloform Reaction Mechanism:
Background image of page 8
The alkylation of an aldehyde or ketone enolate is an example of a nucleophilic substitution reaction. Alkylation of enolates can be difficult to control.
Background image of page 9

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

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 06/25/2009 for the course CHEM 01:160:308 taught by Professor Bokiess during the Spring '09 term at Rutgers.

Page1 / 28

Chapter_18_Enols,_Enolates,_Aldol_(Lectures_11_&_12)...

This preview shows document pages 1 - 10. Sign up to view the full document.

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