L. 7 Enols & Aldols Flashcards Preview

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Flashcards in L. 7 Enols & Aldols Deck (10)
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Identify the Alpha Carbon and Hydrogen in a

Ketone and Aldehyde molecule

Ketone ( Two R Carbonyl Groups)

Aldehyde (One Carbonyl group & one Hydrogen)





  • The electron-withdrawing oxygen of the carbonyl weakens the C-H
  • bond the alpha-carbon.
  • The ENOLATE resulting from deprotonation be stabilized by resonance with the carbonyl.


Keytones vs Aldehydes


Keytones are less reactive towards nucleophiles because of

  • steric hindrance coming from the extra R group (alkyl groups in intermediate increase energy)
  • alpha-carbanion destabilization (alkyl group donates electron density to carbanion = less stabilized)


KETO-ENOL Tautomerization

Aldehydes and Ketones exist in the traditional

Keto form  (C=O) and in the less common

Enol form (ene +ol = double bond + Hydroxyl group)

  • Tautomers are Constitutional Isomers that can be interconverted by moving a hydrogen and a double bond. 
  • Enol can be deprotonated to form an ENOLATES. Good nucleophiles. 



Michael Addition

Enolate attacks an alpha-beta unsaturated carbonyl

 creating a bond between both molecules


Kinetic vs Thermodynamic Enolates


 fast, irreversible, low T, strong and sterically hindered base. Less stable.



Slow reversible, high T, weaker smaller bases.

(Attacks more substituted carbon)



Enamine ----> Imine

Are tautomers of imines, like enols, enamines are the less common tautomer


Aldol Condensation Reaction

  • Nucleophilic Addition to carbonyl
  • Aldehyde or Ketone both as electrophile or nucleophile
  • Electrophile = Keto  &.   Nucleophile = Enol
  • Forming carbon-carbon bond = New molecule = ALDOL
  • ALDOL = Alcohol + Aldehyde
  • Enolate is nucleophile
  • 1st = Condensation Reaction
  • 2nd = Dehydration reaction, resulting in cleaved bond between an alpha,beta-carbon.


Retro-Aldol reaction

The reverse of aldol condensation

  • Aq base and heat
  • breaking bonds between alpha and beta carbons
  • stabilized intermediate enolate (hydration)



Aldehyde & Ketone VS other functional groups 


No leaving groups as compared to all other functional groups