NMR kinetic study of ethyl silicate hydrolysis by ammonia in alcoholic solvents

Abstract

Hydrolysis of Si(OC2H5), by ammonia has been investigated using 'H and I3C NMR measurements in alcoholic media. Use of deuterated CD3CD20D and CD30D solvents proves the absence of transesterification by alkoxy exchange between silicate and alcohols. The rate constant increases when CD30D replaces CD3CDZOD as the solvent (k = 2.8 X L mol-' min-' in CD3CD20D; 7.5 X

Assessing Extreme Models of the Stöber Synthesis Using Transients under a Range of Initial Composition

“…Harris (3) assumed that the nucleation rate was proportional to the experimentally mea-(as in acid), the batch Stöber process analyzed by a wide variety of techniques ( 29 Si-NMR, conductivity, Raman spec-sured rate of TEOS consumption, and he avoided the use of solvation repulsion in the aggregation kernel. Although the troscopy, pH monitoring, gas chromatography, 1 H-NMR, 13 C-NMR, and molybdate analysis), shows the unhydrolyzed treatments of Bogush and Zukoski (2) and of Harris (3) differ somewhat on these points, both treatments success-TEOS as the predominant species in solution (1,3,(8)(9)(10)(11)(12). Only the singly hydrolyzed monomer (Si (OEt) 3 (OH)) is fully predicted the average size and size distribution over the limited composition range of Stöber synthesis.…”

Synthesis of novel pyridinium N‐chloramine precursors and its antimicrobial application on cotton fabrics

“…Therefore, iodine counterpart was prepared by reacting with excess NaI in acetone, which was directly reacted with 3‐hydroxypyridine to successfully give compound 10 with moderate yield of 45%. The moderate yield was not expected: (1) we noticed that a large amount of light yellow viscous solid was produced in the reaction system probably due to K 2 CO 3 –promoted hydrolysis/condensation reaction of siloxane . (2) Based on the TLC observations, we proposed that 3‐iodopropyltriethoxysilane may also react with 3‐hydroxypyridine to form a quaternary pyridinium salt, which usually stay on the baseline of TLC plates.…”

Regulating Payload Release from Hybrid Nanocapsules with Dual Silica/Polycaprolactone Shells

“…To explain the origin of the difference of localization of PCL in the nanocapsules, we investigated the effect of PCL on the hydrolysis rate of TEOS by 1 H NMR spectroscopy. In previous works, the kinetics of TEOS hydrolysis was followed by monitoring the concentration of TEOS by 1 H NMR spectroscopy . Chen et al also performed kinetic studies of the hydrolysis and condensation of TEOS by determining the concentration of TEOS by means of gas chromatography and conductometry .…”

“…In previous works, the kinetics of TEOS hydrolysis was followed by monitoring the concentration of TEOS by 1 H NMR spectroscopy. 36 Chen et al also performed kinetic studies of the hydrolysis and condensation of TEOS by determining the concentration of TEOS by means of gas chromatography and conductometry. 37 In another study, Szczepanowicz et al applied 1 H NMR spectroscopy to follow the formation of the silica shell around emulsion droplets, revealing that the reaction rate is strongly dependent on the pH value.…”