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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Comparative study on the hydrolysis kinetics of substituted ethoxysilanes by liquid-state Si-29 NMR
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Comparative study on the hydrolysis kinetics of substituted ethoxysilanes by liquid-state Si-29 NMR

机译：Si-29 NMR研究取代乙氧基硅烷的水解动力学

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摘要

Liquid-state Si-29 NMR was used to investigate the ammonia-catalyzed initial hydrolysis of different substituted ethoxysilanes dissolved in methanol. The following ethoxysilanes were used: tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and dimethyldiethoxysilane (DBS). Their reaction expresses were obtained by assuming first-order in the reactant ethoxysilanes and varying other reactant ammonia and water concentrations. Individual kinetic rate constants for the initial hydrolysis of each ethoxysilanes, the rate-limiting step for total reactions, were calculated, which were independent of any reactant concentration. The results indicated that the steric factors have more important effect on the reactive reactivity than inductive factors, so that the initial hydrolysis rate constants for the studied ethoxysilanes decreased in an unusual order DDS > TEOS > MTES. For these three ethoxysilanes, a common conclusion was drawn that the substitution of the hydroxyl group for the ethoxyl group resulted in a downfield shift. In the case of DDS, however, the trend was opposite to the previous studies in which the hydrolyzed resultants had upfield shift compared with DDS monomer. (C) 2004 Elsevier B.V. All rights reserved.
机译：液相Si-29 NMR用于研究氨催化的溶解在甲醇中的不同取代乙氧基硅烷的初始水解。使用了以下乙氧基硅烷：四乙氧基硅烷（TEOS），甲基三乙氧基硅烷（MTES）和二甲基二乙氧基硅烷（DBS）。通过假定反应物乙氧基硅烷中的第一级并改变其他反应物氨和水的浓度来获得它们的反应表达。计算每种乙氧基硅烷的初始水解的各个动力学速率常数，即总反应的限速步骤，该常数与任何反应物浓度无关。结果表明，空间因素对反应活性的影响比诱导因素更重要，因此所研究的乙氧基硅烷的初始水解速率常数以不寻常的顺序DDS> TEOS> MTES降低。对于这三种乙氧基硅烷，得出一个普遍的结论，即羟基取代乙氧基会导致低场漂移。然而，在DDS的情况下，该趋势与先前的研究相反，在先前的研究中，水解的产物与DDS单体相比具有高场偏移。 （C）2004 Elsevier B.V.保留所有权利。

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