Nucleophilic attacks on carbon–carbon double bonds. Part XII. Addition of amines to electrophilic olefins and reactivity order of the activating groups

Abstract

The kinetics of the addition of morpholine or pyrrolidine to olefins activated by various electron-attracting groups have been measured. From the kinetic data the following reactivity order for X in compounds CH₂CHX has been derived: PhCO > SO₃Ph > CHO > MeCO > CO₂Ph > p-Me·C₆H₄·SO₂ > CO₂Me > CN > CONH₂ > PO(OEt)₂ > p-NO₂·C₆H₄. This order is mainly determined by the activation enthalpies. Reactivity orders in several reactions from the literature are compared, the factors governing them are discussed, and an extended reactivity scale is suggested. It is suggested that pK_a values of the corresponding CH₃X compounds can serve as a reasonable basis for reactivity comparisons, and a linear relationship between log k and pK_a was found.