Reactions of organic phosphates. Part VI. The hydrolysis of aryl phosphates

Abstract

The hydrolysis of monoaryl phosphates shows acid catalysis only if an electron-attracting substituent (e.g., NO,or CH,CO-) is present in the aryl group. There is then a rate maximum at a strong acid concentration in the range 3 -6 ~. A typical rate maximum a t ca. pH 4.0 due to hydrolysis via the monoanion species is observed in all cases. The reactions, both in aqueous strong acid and at pH 4, proceed by phosphorus-oxygen bond fission.Rate maxima in aqueous strong acid are also observed in the hydrolysis of diphenyl and triphenyl phosphates :the reactions atso proceed by phosphorus-oxygen bond fission. The maxima do not arise from complete protonation of the substrate but are apparently the result of a powerful negative electrolyte effect. EXPERIMENTAL Materials.-Disodium phenyl phosphate. A commercial sample (B.D.H.) was purified by recrystallisation from aqueous alcohol.

Pseudo-rotation in the hydrolysis of phosphate esters

“…The general scheme, represented by the principles (a) -(e) above, and illustrated with the mechanism of hydrolysis of methyl ethylene phosphate has proved to have considerable predictive capability and has been verified by numerous investigators (13) Acyc1icarvjphosp. The acid catalyzed hydrolysis of triaryl phosphates shows a maximum in the rate vs. acidity curve (14,15,16). This maximwn has been ascribed to the decrease in the activity of water with increasing concentration of acid.…”

Hydrolysis rate constants and activation parameters for phosphate- and phosphonate-bridged phthalonitrile monomers under acid, neutral and alkali conditions

“…However, due to the presence of organic esters of phosphonic or phosphoric acids in monomer structure a question of hydrolysis resistance of 1 and 2 naturally came up. Hydrolysis of triesters of phosphoric and phosphonic acids is barely reported in literature [6] , [7] . Here the data on hydrolysis kinetics of 1 and 2 in three different pH values 4, 7 and 10 is presented including rate constants and activation parameters calculated from Arrhenius equation.…”

The mechanisms of hydrolysis of glycosides and their revelance to enzyme-catalysed reactions

“…However, the general use of the Hamm ett criterion has led to difficulties. Many reactions fit neither mechanistic category and some show bizarre behaviour in which the plot of rate coefficient against acidity is a curve with a well-defined maximum (Barnard et al 1966). In a comprehensive review of the subject Bunnett (1961) has pointed out th a t equation (1) can be readily transformed, by using the definition of hQ , into equation ( 3 The mechanisms of hydrolysis of glycosides transition state.…”