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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Rapid hydrolysis of model phosphate diesters by alkaline-earth cations in aqueous DMSO: speciation and kinetics
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Rapid hydrolysis of model phosphate diesters by alkaline-earth cations in aqueous DMSO: speciation and kinetics

机译：DMSO水溶液中碱土阳离子快速水解模型磷酸二酯的形态和动力学

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摘要

Kinetics of the cleavage of two phosphate diesters, bis(4-nitrophenyl) phosphate and 2-hydroxypropyl 4-nitrophenyl phosphate and a triester, 4-nitrophenyl diphenyl phosphate, in the presence of Mg(II), Ca(II) and Sr(II) were studied in 90% vol. DMSO at 37 degrees C. The alkaline hydrolysis of the triester was inhibited by all cations, but with both phosphodiesters strong catalytic effects were observed. Potentiometric titrations of metal perchlorates by Bu4N(OH) revealed formation of M-2(OH)(3+), M(OH)(+), M(OH)(2) and M-2(OH)(5)(-) species. Rate constants for phosphodiester cleavage by individual species were obtained from analysis of rate-concentration profiles. Observed first-order rate constants in the presence of 1-2 mM Mg(II) or Ca(II) in neutral and weakly basic solutions were 10(8)-10(11) times higher than those for background hydrolysis at the same pH while in water additions of up to 50 mM metal produced < 100-fold accelerations. Possible structures of DMSO solvated catalyst-substrate complexes were modeled by DFT calculations with Mg( II). The increased catalytic activity in 90% DMSO is attributed to stronger association of hydroxide ions and anionic phosphodiesters with metal ions and to preferable solvation of cations by DMSO, which creates favorable for reaction anhydrous microenvironment in the coordination sphere of the catalyst.
机译：在Mg（II），Ca（II）和Sr（）存在下，两种磷酸二酯磷酸双（4-硝基苯基）和2-羟丙基4-硝基苯基磷酸酯和三酯4-硝基苯基磷酸二酯的裂解动力学II）以90％vol。 DMSO在37摄氏度下进行。三酯的碱性水解受到所有阳离子的抑制，但在两种磷酸二酯中均观察到强催化作用。用Bu4N（OH）电位滴定金属高氯酸盐显示形成M-2（OH）（3 +），M（OH）（+），M（OH）（2）和M-2（OH）（5）（ -）物种。从速率-浓度曲线分析中获得了单个物种裂解磷酸二酯的速率常数。在中性和弱碱性溶液中存在1-2 mM Mg（II）或Ca（II）时观察到的一级速率常数比在相同pH下背景水解的一级速率常数高10（8）-10（11）倍而在水中添加多达50 mM的金属产生的加速度小于100倍。用Mg（II）通过DFT计算对DMSO溶剂化的催化剂-底物复合物的可能结构进行建模。在90％DMSO中提高的催化活性归因于氢氧根离子和阴离子磷酸二酯与金属离子之间的更强缔合，以及由于DMSO对阳离子的优选溶剂化作用，这为催化剂的配位领域中的反应无水微环境创造了有利条件。

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