Storage Stability of Solvent-Free Condensates of Functionalized Trialkoxysilanes

ABSTRACTThe lack of storage stability of organic-inorganic solvent-free sols is a well-known problem. We investigated the influence of different solvents in the acid catalyzed hydrolysis of various sols on their storage stability. Our experiments were based on two different silanes, 3-methacryloxypropyltrimethoxysilane (MPTS) and 1,1,1-tris(allyloxymethyl)-l-[[[3-(triethoxysilyl)propyl]aminocarbonyl]oxymethyl]methane (silane 31), synthesized by reaction of pentaerythritol triallyl ether and 3-isocyanatopropyltriethoxysilane. The employed solvents were alcohol, tetrahydofuran and tert-butyl methyl ether in a range of 95 wt% to 30 wt% in solution. In order to get comparable chemical conditions the degree of condensation of the various sols were adjusted between 75% and 85%. Furthermore, the sols were modified by silylation with trimethylchlorosilane. A comparison of silylated and not silylated silane 31 clearly showed that a decrease in residual silanol groups increase the storage stability. The results of the investigations demonstrated that both the kind and the amount of solvent used in hydrolysis affects the initial viscosity of solvent-free condensates of silane 31 and MPTS.

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Acid-catalysed hydrolysis of t-butyl methyl ether

Australian Journal of Chemistry ◽

10.1071/ch9681355 ◽

1968 ◽

Vol 21 (5) ◽

pp. 1355

Author(s):

PS Harrison ◽

VR Stimson

Keyword(s):

Methyl Ether ◽

Hydrolysis Of ◽

Butyl Methyl Ether

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Kinetics of the Acid-catalyzed Hydrolysis of 4-(p-Sulfophenylazo)-1-naphthyl Methyl Ether and 4-(p-Sulfophenylazo)-anisole1

Journal of the American Chemical Society ◽

10.1021/ja01466a028 ◽

1961 ◽

Vol 83 (5) ◽

pp. 1117-1123 ◽

Cited By ~ 12

Author(s):

J. F. Bunnett ◽

Erwin Buncel

Keyword(s):

Methyl Ether ◽

Acid Catalyzed ◽

Kinetics Of ◽

Hydrolysis Of

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The effect of polymeric and model imidazolium halides on the rate of hydrolysis of 4-acetoxy-3-nitrobenzoic acid

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19850845 ◽

1985 ◽

Vol 50 (4) ◽

pp. 845-853 ◽

Cited By ~ 3

Author(s):

Miloslav Šorm ◽

Miloslav Procházka ◽

Jaroslav Kálal

Keyword(s):

Catalyst Concentration ◽

Low Molecular Weight ◽

Imidazolium Chloride ◽

First Order ◽

Nitrobenzoic Acid ◽

Rate Of Hydrolysis ◽

Acid Catalyzed ◽

Hydrolysis Of ◽

Ethanol In Water ◽

Direct Attack

The course of hydrolysis of an ester, 4-acetoxy-3-nitrobenzoic acid catalyzed with poly(1-methyl-3-allylimidazolium bromide) (IIa), poly[l-methyl-3-(2-propinyl)imidazolium chloride] (IIb) and poly[l-methyl-3-(2-methacryloyloxyethyl)imidazolium bromide] (IIc) in a 28.5% aqueous ethanol was investigated as a function of pH and compared with low-molecular weight models, viz., l-methyl-3-alkylimidazolium bromides (the alkyl group being methyl, propyl, and hexyl, resp). Polymers IIb, IIc possessed a higher activity at pH above 9, while the models were more active at a lower pH with a maximum at pH 7.67. The catalytic activity at the higher pH is attributed to an attack by the OH- group, while at the lower pH it is assigned to a direct attack of water on the substrate. The rate of hydrolysis of 4-acetoxy-3-nitrobenzoic acid is proportional to the catalyst concentration [IIc] and proceeds as a first-order reaction. The hydrolysis depends on the composition of the solvent and was highest at 28.5% (vol.) of ethanol in water. The hydrolysis of a neutral ester, 4-nitrophenyl acetate, was not accelerated by IIc.

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Benzyl ethers of methyl α-D-glucopyranoside

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19801959 ◽

1980 ◽

Vol 45 (7) ◽

pp. 1959-1963 ◽

Cited By ~ 1

Author(s):

Dušan Joniak ◽

Božena Košíková ◽

Ludmila Kosáková

Keyword(s):

Kinetic Study ◽

Spectrophotometric Determination ◽

Reductive Cleavage ◽

Ether Bond ◽

Benzyl Ethers ◽

Acid Catalyzed ◽

Model Substances ◽

Hydrolysis Of

Methyl 4-O-(3-methoxy-4-hydroxybenzyl) and methyl 4-O-(3,5-dimethoxy-4-hydroxybenzyl)-α-D-glucopyranoside and their 6-O-isomers were prepared as model substances for the ether lignin-saccharide bond by reductive cleavage of corresponding 4,6-O-benzylidene derivatives. Kinetic study of acid-catalyzed hydrolysis of the compounds prepared was carried out by spectrophotometric determination of the benzyl alcoholic groups set free, after their reaction with quinonemonochloroimide, and it showed the low stability of the p-hydroxybenzyl ether bond.

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Cyclization and acid-catalyzed hydrolysis of O-benzoylbenzamidoximes

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19862786 ◽

1986 ◽

Vol 51 (12) ◽

pp. 2786-2797

Author(s):

František Grambal ◽

Jan Lasovský

Keyword(s):

Reaction Rate ◽

Kinetic Isotope ◽

Acid Base Equilibrium ◽

Mineral Acids ◽

Kinetics Of Formation ◽

Acid Catalyzed ◽

Ph Scale ◽

Kinetics Of ◽

Hydrolysis Of ◽

Derivatives Of

Kinetics of formation of 1,2,4-oxadiazoles from 24 substitution derivatives of O-benzoylbenzamidoxime have been studied in sulphuric acid and aqueous ethanol media. It has been found that this medium requires introduction of the Hammett H0 function instead of the pH scale beginning as low as from 0.1% solutions of mineral acids. Effects of the acid concentration, ionic strength, and temperature on the reaction rate and on the kinetic isotope effect have been followed. From these dependences and from polar effects of substituents it was concluded that along with the cyclization to 1,2,4-oxadiazoles there proceeds hydrolysis to benzamidoxime and benzoic acid. The reaction is thermodynamically controlled by the acid-base equilibrium of the O-benzylated benzamidoximes.

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Crystal Structures of Two New Cyclosporin Clathrates

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20001950 ◽

2000 ◽

Vol 65 (12) ◽

pp. 1950-1958 ◽

Cited By ~ 2

Author(s):

Michal Hušák ◽

Bohumil Kratochvíl ◽

Ivana Císařová ◽

Alexandr Jegorov

Keyword(s):

Crystal Structures ◽

Methyl Ether ◽

Van Der Waals ◽

Van Der Waals Interactions ◽

Solvent Molecules ◽

Butyl Methyl Ether

Two isomorphous clathrates formed by dihydrocyclosporin A or cyclosporin V with tert-butyl methyl ether are reported and compared with the structures of related P21-symmetry cyclosporin clathrates. The cyclosporin molecules in both structures are associated via van der Waals interactions forming cavities occupied by solvent molecules (cyclosporin : tert-butyl methyl ether is 1 : 2).

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