Phosphoryl transfer reactions phosphate monoesters dianions

Uncatalyzed Reactions of Phosphate Monoesters. Phosphate monoesters in physiologically relevant pH ranges exist as either the monoanion or dianion. A large body of evidence indicates that uncatalyzed phosphoryl transfer reactions of both ionic forms takes place by loose transition states that are characterized by extensive bond cleavage to the leaving group and a small degree of bond formation to the nucleophile (for reviews of the evidence, see References (3,4)). Despite loose transition states, these reactions are concerted, and free metaphosphate is not formed in protic solvents (5). 

Ramirez and Marecek have investigated the solvolyses of 2,4-dinitrophenyl phosphate in aprotic and protic solvents and described reaction conditions that are consistent with the involvement of free metaphosphate anion 45, 46). In particular, the dianion of the reactive phosphate monoester is capable of transferring its phosphoryl group to /err-butanol whereas the monoanion of the same ester is essentially unreactive in the same reaction. Since rert-butanol is unreac-tive as a nucleophile for steric reasons, the phosphorylation of this alcohol is considered to be a diagnostic test for the involvement of the highly reactive metaphosphate anion. 

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