Mark Bishop

Analytical Chemistry and

Signal Acquisition/Analysis



Introduction
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Introduction


α, β - Unsaturated Carbonyl Compounds

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Carbon-carbon double bond is deactivated towards electrophilic addition by the electron withdrawing carbonyl group. However, the double bond is activated towards nucleophilic addition. In electrophilic addition the intermediate is a cation. In nucleophilic addition the intermediate is an anion. Addition to the carbon-carbon double bond takes place with orientation of the negative addition species adding to the β-carbon and the positive species adding to the α-carbon.

Electrophilic addition

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Nucleophilic addition

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The Michael Addition

The Michael addition involves the formation of a carbanion through the abstraction of the acidic hydrogen (by a base) from the following three compounds.

Ethyl malonate:

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Ethyl acetoacetate

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Ethyl cyanoacetate

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The nucleophile thus formed can then combine with an α, β-unsaturated carbonyl compound. For example:

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The Diels-Alder Reaction

A cycloaddition of a conjugated diene and an α, β-unsaturated carbonyl compound.

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For example:

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Quinones are an example of a highly conjugated α, β-unsaturated carbonyl compound:

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