L. 7 Enols & Aldols Flashcards Preview

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Flashcards in L. 7 Enols & Aldols Deck (10)
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1

Identify the Alpha Carbon and Hydrogen in a

Ketone and Aldehyde molecule

Ketone ( Two R Carbonyl Groups)

Aldehyde (One Carbonyl group & one Hydrogen)

2

Alpha-Hydrogens

(Properties)

 

  • 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.

3

Keytones vs Aldehydes

(Reactivity) 

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)

4

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. 

 

5

Michael Addition

Enolate attacks an alpha-beta unsaturated carbonyl

 creating a bond between both molecules

6

Kinetic vs Thermodynamic Enolates

Kinetic;

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

 

Thermodynamic;

Slow reversible, high T, weaker smaller bases.

(Attacks more substituted carbon)

7

Enamines

Enamine ----> Imine

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

8

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.

9

Retro-Aldol reaction

The reverse of aldol condensation

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

 

10

Aldehyde & Ketone VS other functional groups 

(reaction)

No leaving groups as compared to all other functional groups