Preparation and chromatographic evaluation of columns for reversed-phase liquid chromatography
Column selection in reversed-phase liquid chromatography is still not a straightforward process. In this study, we have evaluated and compared the performance of several traditional C18 phases with polar-modified phases and found distinct differences in the chromatographic behavior between two groups, as well as a high degree of variability within each group. The polar-endcapped phases exhibit similar hydrophobic selectivity, higher hydrogen bonding capacities and silanol activity with reference to the conventional C18 columns. The polar-embedded phases displayed a greatly reduced hydrophobic nature and a significantly reduced silanol activity compared to the conventional C18 phases. It appears that ionic and/or dipole interactions play a significant role in the overall retention behavior of the polar-modified phases towards basic and acidic analytes.
Isomerization in the reaction of (aminoalkyl)trialkoxysilanes with carboxylic acid anhydrides
The products of the reactions of monofunctional (3-aminopropyl) triethoxysilane and (3-aminopropyl)trimethoxysilane and bifunctional [3-N-(2-aminoethyl)aminopropyl]trimethoxysilane with acetic and maleic anhydrides in CCl4 at varied reagent molar ratios are studied by 1H and 13C NMR spectroscopy. It is shown that the reaction of [3-N-(2-aminoethyl)aminopropyl]trimethoxysilane with the above anhydrides leads to formation of diamides as mixtures of cisoid and transoid rotamers about both amide bonds. The reactions with monofunctional (aminopropyl) trialkoxysilanes give individual isomers.
Kovyazin,Nikitin,Kopylov,Sokol'skaya
p. 47 - 54
(2008/02/13)
PROCESS FOR PRODUCING ORGANOALKOXYSILANES FROM ORGANIC ACIDS OR CYANATES AND HALOALKYLALKOXYSILANES
A process for the preparation of organoalkoxysilanes containing one or more organic functional groups derived from organic acids or hydrogen cyanates, by a continuous or batch process utilizing a solid guanidinium salt as a phase transfer catalyst for the reaction between a liquid phase haloalkylalkoxysilane and a solid phase alkali or alkaline earth metal salt or ammonium salt of an organic acid or a metal cyanate.
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Page/Page column 5
(2010/11/25)
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