名称:
                                The E1cB mechanism in the alkaline hydrolysis of N,N-diethyl-P-(3,5-dimethyl-4-hydroxyphenyl)phosphonamidic chloride
                             
                            
                                摘要:
                                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(a)K(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(N)2(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.