THEORY OF DIFUNCTIONAL COMPOUNDS

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THEORY OF DIFUNCTIONAL COMPOUNDS
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The 3-keto esters or β -keto esters are obtained by the Claisen condensation of two esters.

Diesters produce cyclic 3-ketoesters by intramolecular Claisen condensation, also called Dieckmann condensation
Mixed Claisen produces 1,3-dicarbonyl compounds by condensation between ketone and ester.
  • Obtaining 3-ketoesters

condensation claisen 1

Mechanism:

condensation claisen 2

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THEORY OF DIFUNCTIONAL COMPOUNDS
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Ethyl 3-oxobutanoate (ethyl acetylacetate), can be obtained by Claisen from ethyl acetate, and is a very efficient reagent for the preparation of ketones.

 
sintesis-acetilacetica
 

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THEORY OF DIFUNCTIONAL COMPOUNDS
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Malonic synthesis is a method that allows obtaining carboxylic acids. This synthesis starts with diethyl propanedioate (diethyl malonate).

 
sintesis-malonica

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THEORY OF DIFUNCTIONAL COMPOUNDS
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When the electrophile used in the acetylacetic or malonic synthesis is a,b -unsaturated, a 1,5-dicarbonyl will be formed, this type of reaction is called Michael addition.

michael addition 1

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The use of aldehydes and ketones in the acetylacetic or malonic synthesis allows obtaining ketones or a,b -unsaturated acids.

condensation knoevenagel 1

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THEORY OF DIFUNCTIONAL COMPOUNDS
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Acyloinic condensation transforms esters into alpha-hydroxyketones. This reaction is carried out with sodium metal in an inert solvent.

acyloionic condensation 1

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Benzoin condensation yields a -hydroxycarbonyls by reaction of aromatic aldehydes with sodium cyanide.

benzoinic condensation 01

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THEORY OF DIFUNCTIONAL COMPOUNDS
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The reaction of aldehydes with 1,3-dithiacyclohexane, in the presence of Lewis acids, produces 1,3-dithianes that have hydrogens that can be subtracted with strong bases, forming the 1,3-dithiane anion. These anions are very good nucleophiles and react with a wide range of electrophiles.

Let's see how to obtain 2-butanone from ethanal.
synthesis 13 days 01

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THEORY OF DIFUNCTIONAL COMPOUNDS
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1,2-Dicarbonyl compounds can be prepared by oxidation of α-hydroxycarbonyls.

synthesis 12 dicarbonyls 01