SOLVOLYSIS OF SOME PHOSPHORAMIDIC HALIDES - QUESTION OF METAPHOSPHORIMIDATE INTERMEDIATES

The solvolytic studies on methyl N-cyclohexylphosphoramidothioic chloride are extended and compared with some closely related phosphoramidic chlorides. It is shown that the basic hydrolysis of the former in aqueous methanol shows clear borderline behaviour between a solvent assisted displacement on the anion and a true SN 1 (P) reaction. Strong evidence is presented to indicate that the monomeric metaphosphorimidothioate intermediate reacts preferentially with methanol in the mixed system. From a comparison of the rates of solvolysis of the corresponding P=O chloride with the above and other related compounds it is deduced that although the base solvolysis of this proceeds via the anion a metaphosphorimidate intermediate is highly improbable. Arguments are advanced to suggest that monomeric metaphosphate esters will not be important reaction intermediates.