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PTT 102 Organic Chemistry Sem I 2012/2013 PowerPoint Presentation
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Rozaini Abdullah School of Bioprocess Eng UniMAP Week 10. PTT 102 Organic Chemistry Sem I 2012/2013. Outline. Aldol. Carbonyl Condensation Micheal Reaction. Claisen. 1. Carbonyl Condensation.

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outline
Outline

Aldol

  • Carbonyl Condensation
  • Micheal Reaction

Claisen

1 carbonyl condensation
1. Carbonyl Condensation
  • Carbonyl compounds are both the electrophile and nucleophile in carbonyl condensation reactions
aldol condensation
Aldol Condensation
  • Acetaldehyde reacts in basic solution (NaOEt, NaOH) with another molecule of acetaldehyde
  • The b-hydroxyaldehydeproduct is aldol (aldehyde + alcohol)
  • This is a general reaction of aldehydes andketones
mechanism of aldol reactions
Mechanism of Aldol Reactions
  • Aldol reactions, like all carbonyl condensations, occur by nucleophilic addition of the enolate ion of the donor molecule to the carbonyl group of the acceptor molecule
  • The addition intermediate is protonated to give an alcohol product
predicting aldol products
Predicting Aldol Products

The product will have an alcohol and a carbonyl in a 1,3 relationship (a beta-hydroxy carbonyl)

1 claisen condensation
1. Claisen Condensation
  • Condensation of Two Ester Molecules.
  • The product of a Claisen condensation is a β-keto ester.
  • In a Claisen condensation, one molecule of carbonyl compound is the nucleophile and second molecule is electrophile.
  • The new C-C bond connect the α-carbon of one molecule and the carbon that was formerly the carbonyl carbon of the other molecule
mechanism of the claisen condensation
Mechanism of the ClaisenCondensation
  • Similar to aldol condensation: nucleophilicacyl substitution of an ester enolate ion on the carbonyl group of a second ester molecule
  • If the starting ester has more than one acidic a hydrogen, the product -keto ester has a doubly activated proton that can be abstracted by base
  • Requires a full equivalent of base rather than a catalytic amount
  • The deprotonation drives the reaction to the product
learning check
Learning Check:

Predict the product of Claisen condensation of ethyl propanoate

solution
Solution:

Predict the product of Claisen condensation of ethyl propanoate

mixed claisen condensations
Mixed Claisen Condensations
  • Successful when one of the two esters acts as the electrophilic acceptor in reactions with other ester anions to give mixed -keto esters
2 conjugate carbonyl additions the michael reaction
2.Conjugate Carbonyl Additions: The MichaelReaction
  • Enolates can add as nucleophiles to ,-unsaturated aldehydes and ketones to give the conjugate addition product
mechanism of the michael
Mechanism of the Michael
  • Nucleophilic addition of a enolate ion donor to the  carbon of an ,-unsaturated carbonyl acceptor
learning check1
Learning Check:
  • Make the following using a Michael Reaction:
solution1
Solution:
  • Make the following using a Michael Reaction:
slide18

Learning Check:

Which of the following statements explains why the following aldehyde will not undergo an aldol reaction with itself?
  • The benzene ring makes the carbonyl group unreactive towards aldol reactions.
  • A carbonyl group must be connected to two alkyl groups in order to undergo an aldol reaction.
  • The molecule does not possess any hydrogens α to the carbonyl group.
  • Electrophilic aromatic substitution competes favorably with the aldol reaction.
  • Nucleophilic acyl substitution competes favorably with the aldol reaction.
slide19
Which of the following statements explains why the following aldehyde will not undergo an aldol reaction with itself?

Solution:

  • The benzene ring makes the carbonyl group unreactive towards aldol reactions.
  • A carbonyl group must be connected to two alkyl groups in order to undergo an aldol reaction.
  • The molecule does not possess any hydrogens α to the carbonyl group.
  • Electrophilic aromatic substitution competes favorably with the aldol reaction.
  • Nucleophilic acyl substitution competes favorably with the aldol reaction.
what type of reaction occurs in a claisen condensation
What type of reaction occurs in a Claisen condensation?

Learning Check:

  • electrophilic aromatic substitution
  • nucleophilic addition
  • hydrolysis
  • nucleophilicacyl substitution
  • decarboxylation
what type of reaction occurs in a claisen condensation1
What type of reaction occurs in a Claisen condensation?

Solution:

  • electrophilic aromatic substitution
  • nucleophilic addition
  • hydrolysis
  • nucleophilicacyl substitution
  • decarboxylation
select the correct claisen condensation product for the following reaction

1.

2.

3.

5.

4.

Select the correct Claisen condensation product for the following reaction.

Learning Check:

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  • 5