A reappraisal of the role of the E1cB mechanism of hydrolysis of phosphoramidic derivatives

Abstract

Rates of alkaline solvolysis of a series of aryl methyl phosphoramidates and phosphoramidothioates have been measured; the results lead to the conclusion that, despite considerable differences in rate with varying degree of N-substitution, there is no important contribution from an E1cB process such as operates for related phosphoramidic halides and acyl carbamates. On the basis of the results of studies on the relative rates and direction of cleavage in the basic solvolysis of some OS-dimethyl phosphoramidothioates and phosphoramidodithioates it is proposed, contrary to an earlier suggestion, that both P–O and P–S cleavage arise predominantly from nucleophilic attack, although some contribution to the latter may arise from an elimination mechanism.