Fission of Activated Carbon-Nitrogen and Carbon-Sulphur Bonds. V. Polarographic Study of Elimination of β-Morpholino Propiophenone

Abstract

Mannich bases of the β-amino ketone type undergo elimination only in the unprotonated free base form. With stronger bases like β-piperidino propiophenone the elimination reaction is complicated by the consecutive reaction of the resulting vinyl ketone with hydroxyl ions. However, with weaker bases like β-morpholino propiophenone the simple elimination process can be studied as the vinyl ketone formed is stable in the lower pH-range in which now the reaction proceeds. Owing to the competitive effects of fastly established equilibria of protonation of the Mannich base and of the amine formed the reaction corresponds to reversible or irreversible kinetics according to pH-value. The values k ₁ = (5·5 ± 1) · 10⁻⁵ s⁻¹ for elimination, k ₋₁ = (20 ± 5) 1 mol⁻¹ s⁻¹ for addition reaction and K = k ₋₁/k ₁ = = (4 ± 1) · 10⁵ for the equilibrium constant have been found.

Part IV. (erroneously denoted as Part III.): This Journal 28, 1614 (1963).