- Direct observation of growth defects in zeolite beta
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High-resolution transmission electron microscopy reveals linear, "double pore" defects in the important zeolite beta. Structural interpretation of these defects gives evidence for the mechanism by which the zeolite crystallizes. Copyright
- Wright, Paul A.,Zhou, Wuzong,Perez-Pariente, Joaquin,Arranz, Mar
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- Benzylation Reactions in DMF Lead to an Impurity Which Acts as an Organocatalyst Poison in Thiourea-Catalyzed Glycosylations
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The benzylation of alcohols with the commonly used combination of benzyl bromide and sodium hydride in DMF can lead to the formation of an amine side product, N,N′-dimethyl-1-phenyl-1-(o-tolyl)methanamine. This amine coeluted with benzylated galactal during column chromatography and was found to be a catalyst poison in thiourea-catalyzed glycosylations of galactals. It may also be problematic for other base-sensitive reactions involving benzylated substrates. Solutions to this problem are described.
- Colgan, Avene C.,Müller-Bunz, Helge,McGarrigle, Eoghan M.
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- Synthesis, characterization and thermal properties of nine quaternary dialkyldiaralkylammonium chlorides
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Nine R2 R2′ N+ Cl- (R=benzyl, 2-methylbenzyl, 3-methylbenzyl, 4-methylbenzyl, 2-phenylethyl or 3-phenylpropyl; R′=ethyl or methyl) quaternary dialkyldiaralkylammonium chlorides were synthesized by treating dimethylformamide or diethylformamide with non-substituted or substituted arylalkyl (aralkyl) halide in the presence of sodium carbonate. The 1H NMR, 13C NMR spectroscopy, mass spectroscopy and elemental analysis were used to characterize the synthesized products. The crystal structures of six compounds were determined by X-ray single crystal diffraction. Four of the compounds crystallized in monoclinic space groups C2/c and P21/c (or P21/n), one in triclinic space group P-1 and one in orthorhombic space group Pbca. The powder diffraction method was used to compare the structural similarities between the single crystal and the microcrystalline bulk composition. Thermal properties of the new compounds were studied using TG/DTA and DSC methods. The decomposition of the compounds started generally between 130-185 °C and occurred without identifiable cleavages. The synthesized compounds do not seem to be suitable for ionic liquid applications because no melting point was observed for most of them. However, the good thermal stability of these compounds enables their potential use for example as phase-transfer catalysts and electrolytes.
- Busi, Sara,Lahtinen, Manu,K?rn?, Minna,Valkonen, Jussi,Kolehmainen, Erkki,Rissanen, Kari
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- Novel one-pot synthesis of quaternary ammonium halides: New route to ionic liquids
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Treatment of an amide with an alkyl or substituted alkyl halide in the presence of a weak base in a one-pot reaction leads to crystalline quaternary ammonium halides with reasonable chemical yields; some of the compounds show low melting points and a liquid range of over 50-100°C before decomposition.
- Ropponen, Jarmo,Lahtinen, Manu,Busi, Sara,Nissinen, Maija,Kolehmainen, Erkki,Rissanen, Kari
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