Abstract: Intramolecular displacement reactions at phosphorus have been examined in a series of N-alkyl-0-(arylphenylphos-phory1) ethanolamines in 45% dioxane-water (v/v) at 35 OC. The examination of the pH-rate profiles, the detection of external buffer catalysis, and the observation of deuterium solvent effects reveal the concurrent operation of three types of P-0 bond cleavage mechanisms: electrostatic catalysis by the protonated ammonium ...