The E1cB Mechanism in the Alkaline Hydrolysis of N,N-Diethyl-P-(3,5-dimethyl-4-hydroxyphenyl)phosphonamidic Chloride

Article abstract of DOI:10.1021/jo00001a016

The alkaline hydrolysis of the title compound 1 proceeds via an E1cB mechanism.A tricoordinate phosphorus species intermediate 3, or a metaphosphate-like transition state, constitutes the best hypothesis accounting for the observed kinetic results.The apparent bimolecular rate constant for the attack of hydroxide ion on the neutral 4-hydroxy-substituted chloride (k_aK_a/K_w) is more than 5 orders of magnitude larger than the true bimolecular rate constant for the attack of HO^- on the corresponding methoxy chloride 2 which possesses the S_N2(P) mechanism.Support of the E1cB mechanism proposed for 1 comes also from activation entropy studies and by the effect of added nitrogen nucleophiles on reaction rates.