Kinetic medium effects. IV. Hydrolysis of trimethyl phosphate in mixed solvents

Abstract

The rate of hydrolysis of trimethyl phosphate (tmp) has been measured at 90.5� as a function of solvent composition in water-dimethyl sulphoxide and water-ethylene glycol mixtures. The rate constant of the "spontaneous" hydrolysis decreases with decreasing water content; an acid-catalysed reaction, whose rate constant increases with decreasing water content, becomes dominant at low water concentrations. Solvent isotope effects in D2O have been measured for both the spontaneous and acid-catalysed reactions, and are close to unity in each case. Salt effects have also been studied In aqueous sodium nitrate and perchlorate solutions, and are found to be small. Reaction mechanisms are discussed in the light of the results obtained.

Silica-bound copper(ii)triazacyclononane as a phosphate esterase: effect of linker length and surface hydrophobicity

“…The rate decrease occurred at approximately 15% conversion; thus, the cause was not exhaustion of the supply of substrate. We surmised that the rate decrease was due to product inhibition since such a phenomenon was observed for homogeneous Cu [9]aneN 3 Cl 2 -mediated BNPP hydrolysis in aqueous solution. 30 That this decrease was indeed due to product inhibition was supported by a recycling experiment.…”

“…One strategy was the use of mixed solvents, which exploited the different solubility preferences of catalyst, substrate and product to facilitate recycling of the catalyst. 9 A disadvantage of this method was that as the percentage of water in the mixed solvent system decreased, so did the hydrolytic activity, an unsurprising result since the water was the sole nucleophile. Modifications to this mixed solvent technique naturally led to addition of hydrolysis-promoting species to the system to provide a better nucleophile than water.…”

“…Among transition metal-based hydrolytic agents, copper(II) complexes were often the fastest, 28 and Cu(II) is known for its high binding affinity in coordination complexes. The complex Cu [9]aneN 3 Cl 2 , with a binding affinity of 10 15.5 for the [9]aneN 3 ligand, 29 hydrolyzes the phosphate ester bond of simple activated phosphodiesters, 30-32 phosphotriesters 33 and cleaves the phosphate ester backbone of DNA and RNA. 34, 35 Heterogeneous copper(II) triazacyclononane hydrolysis agents were reported: poly(ethylene glycol)-supported (Cu [9]aneN 3 ) 2+8 and silica-bound (Cu [9]aneN 3 ) 2+ hydrolyzed phosphodiesters, 36 polymer-bound (Cu [9]aneN 3 ) 2+ hydrolyzed both phosphodiesters and phosphotriesters 6 and nanoparticles bearing (Cu [9]aneN 3 ) 2+ promoted transesterification.…”

“…The complex Cu [9]aneN 3 Cl 2 , with a binding affinity of 10 15.5 for the [9]aneN 3 ligand, 29 hydrolyzes the phosphate ester bond of simple activated phosphodiesters, 30-32 phosphotriesters 33 and cleaves the phosphate ester backbone of DNA and RNA. 34, 35 Heterogeneous copper(II) triazacyclononane hydrolysis agents were reported: poly(ethylene glycol)-supported (Cu [9]aneN 3 ) 2+8 and silica-bound (Cu [9]aneN 3 ) 2+ hydrolyzed phosphodiesters, 36 polymer-bound (Cu [9]aneN 3 ) 2+ hydrolyzed both phosphodiesters and phosphotriesters 6 and nanoparticles bearing (Cu [9]aneN 3 ) 2+ promoted transesterification. 13 In this report, we describe new silica-bound (Cu [9]aneN 3 ) 2+ materials with varying material properties, which were synthesized and tested for reactivity toward phosphate ester hydrolysis.…”

“…34, 35 Heterogeneous copper(II) triazacyclononane hydrolysis agents were reported: poly(ethylene glycol)-supported (Cu [9]aneN 3 ) 2+8 and silica-bound (Cu [9]aneN 3 ) 2+ hydrolyzed phosphodiesters, 36 polymer-bound (Cu [9]aneN 3 ) 2+ hydrolyzed both phosphodiesters and phosphotriesters 6 and nanoparticles bearing (Cu [9]aneN 3 ) 2+ promoted transesterification. 13 In this report, we describe new silica-bound (Cu [9]aneN 3 ) 2+ materials with varying material properties, which were synthesized and tested for reactivity toward phosphate ester hydrolysis. We observe that the length of the linker and the hydrophobicity of the surface influences the rate of hydrolysis.…”