Mark Bishop

Analytical Chemistry and

Signal Acquisition/Analysis



α, β - Unsaturated Carbonyl Compounds

no image available

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

no image available

Nucleophilic addition

no image available

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:

no image available

Ethyl acetoacetate

no image available

Ethyl cyanoacetate

no image available

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

no image available

The Diels-Alder Reaction

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

no image available

For example:

no image available

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

no image available
ID may be exposed