Rate and product studies with dimethyl phosphorochloridate and phosphorochloridothionate under solvolytic conditions

The specific rates of solvolysis of dimethyl phosphorochloridate and of dimethyl phosphorochloridothionate are very well correlated using the extended Grunwald-Winstein equation, with incorporation of the NT solvent nucleophilicity scale and the YCl solvent ionizing power scale. The sensitivity parameters (l and m) are similar to each other and also similar to previously recorded values for solvolyses of arenesulfonyl chlorides, which were proposed to follow a concerted displacement mechanism. For solvolyses in aqueous ethanol or aqueous methanol the product selectivities (S) are close to unity. For solvolyses in aqueous 2,2,2-trifluoroethanol, the values are too small to accurately measure, showing a very large preference for product formation involving nucleophilic attack by the water component. It is concluded that the chloride and chloridothionate solvolyses, in common with the solvolyses of arenesulfonyl chlorides, follow a concerted displacement mechanism.