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WWU -- Chemistry The Claisen Ester Condensation Taken from: http://atom.chem.wwu.edu/kriz/org_2 1c.ppt http://atom.chem.wwu.edu/kriz/org_2 1c.ppt
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WWU -- Chemistry The Claisen Ester Condensation Esters, like aldehydes and ketones, have acidic -hydrogens. When an ester bearing an -hydrogen is treated with a strong base, a condensation reaction takes place to yield a -ketoester.
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WWU -- Chemistry The Claisen Ester Condensation NOTE: The alkoxide should match the alkyl group of the ester in order to avoid a competing transesterification.
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WWU -- Chemistry Claisen Ester Condensation -- Mechanism (Part One)
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WWU -- Chemistry Claisen Ester Condensation -- Mechanism (Part Two)
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WWU -- Chemistry The Key to Claisen Ester Condensations The -carbon of the donor attaches itself to the carbonyl carbon of the acceptor. The alkyl group of the acceptor leaves to form a C=O bond.
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WWU -- Chemistry Example
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Another Example
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WWU -- Chemistry Example of a Ring Formation This reaction is known as the Dieckmann cyclization.
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WWU -- Chemistry What if we mixed two different esters? As in the case with the aldol condensation, if we mixed two different esters, the result would be a mixture of products. However, we can do this deliberately, in what is known as a crossed Claisen ester condensation.
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WWU -- Chemistry Crossed Claisen Condensation In the crossed Claisen condensation, we choose one of the esters to be the acceptor. The acceptor does not have -hydrogens. The other ester, the donor, does have - hydrogens. It can react with base to form a nucleophilic enolate ion. With such an experimental design, the crossed Claisen condensation can be used successfully.
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WWU -- Chemistry Crossed Claisen Condensation -- An Example
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WWU -- Chemistry Synthesize this:
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