α,β-unsaturated carbonyl compounds have polarized bonds because carbon and oxygen differ in electronegativity, with the carbon acquiring a partial positive charge and the oxygen acquiring a partial negative charge. Through resonance, the end of the alkene furthest from the carbonyl group also acquires a partial positive charge. Nucleophiles with significant amounts of electron density add to the alkene forming an enolate and a new single bond. The enolate is protonated at carbon to form a new C-H bond and to reform the carbonyl group. Two single bonds are stronger than the original olefin, providing the energy to drive the reaction forward. This reaction is called a Michael addition reaction.