Search results for "Eating"
showing 10 items of 1247 documents
Surface acidity studies on active aluminas by means of the amine titration method and heterogeneous isotopic exchange using HTO
1982
Abstract The maximum sorption capacity of n-butylamine (A + n-but ), the exchange capacity of HTO (A HTO ) and the acid strength distribution (ASD) - titration of n-butylamine using arylmethanols as indicators - were measured for a series of commercial active aluminas. A + n-but was formally regarded as total acidity and was found to be larger than A HTO , the latter representing a measure of the Broensted acidity. On the other hand, the cumulative acidity derived from ASD gave values smaller or equal to A HTO . Changes in A HTO and A + n-but within a series of aluminas manufactured at different calcination temperatures gave the expected results which were also supported by infrared spectro…
Stability−Charge and Stability−Structure Relationships in the Binding of Dicarboxylic Ligands by Open-Chain Polyammonium Cations
2000
The stability of complexes formed by 5 dicarboxylic ligands with 11 open-chain polyammonium cations (40 systems) was studied potentiometrically, in aqueous solution, at 25 °C. In all the systems ALHr species (A = amine, L = dicarboxylic ligand, r = 1 ... n; diamines n = 3, triamines n = 4, tetraamines n = 4 or 5) were found. Formation constants for the various complexes studied in this work, together with data for the analogous systems previously studied (20 systems), were examined as a function of charges involved in the formation reaction and of the structure of both the dicarboxylic ligand and the polyammonium cation. Structure generally has little effect on stability, while charges play…
Well-Defined Multi-Amino-Functional and Stimuli-Responsive Poly(propylene oxide) by Crown Ether Assisted Anionic Ring-Opening Polymerization
2017
Multi-amino-functional poly(propylene oxide) (PPO) copolymers were synthesized by the anionic ring-opening copolymerization (AROP) of N,N-diethyl glycidyl amine (DEGA) and propylene oxide (PO). A solvent free synthesis route using potassium counterions and crown ether for the AROP enabled controlled (co)polymerization with full conversion. The strategy provided access to PPO-b-PDEGA block copolymers, statistical PPO-co-PDEGA copolymers, and, for the first time, PDEGA homopolymer. Molecular weights in the range of 1400 to 4200 g/mol (Mn) and dispersities (Mw/Mn) below 1.1 were obtained. Both the kinetics and resulting microstructure of the statistical copolymerization were investigated by in…
Uranyl(VI) complexes of [O,N,O,N′]-type diaminobis(phenolate) ligands: Syntheses, structures and extraction studies
2008
Abstract The syntheses and crystal structures of four new uranyl complexes with [O,N,O,N′]-type ligands are described. The reaction between uranyl nitrate hexahydrate and the phenolic ligand [(N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-N′,N′-dimethylethylenediamine)], H2L1 in a 1:2 molar ratio (M to L), yields a uranyl complex with the formula [UO2(HL1)(NO3)] · CH3CN (1). In the presence of a base (triethylamine, one mole per ligand mole) with the same molar ratio, the uranyl complex [UO2(HL1)2] (2) is formed. The reaction between uranyl nitrate hexahydrate and the ligand [(N,N-bis(2-hydroxy-3,5-di-t-butylbenzyl)-N′,N′-dimethylethylenediamine)], H2L2, yields a uranyl complex with the formula [UO…
Dinuclear bis(terpyridine)ruthenium(II) complexes by amide coupling of ruthenium amino acids: Synthesis and properties
2011
Abstract Two redox-asymmetric amide-bridged bis(terpyridine)ruthenium(II) complexes (3a, 3b) have been prepared by amide coupling of a carboxylic acid functionalized complex with an amine substituted complex and they were fully characterized by spectroscopic analyses. They emit at 692 and 750 nm at room temperature in fluid solution with quantum yields larger than 10−3 and 3MLCT lifetimes of 22 ns. Ru···Ru distances were estimated from DFT models as 17.7 and 13.4 A for 3a and 3b, respectively. Cyclic voltammetry gives two oxidation potentials for the differently substituted ruthenium sites with splittings of 0.10 and 0.23 V for 3a and 3b, respectively. Oxidation of 3b with CeIV ions gives t…
A two-step synthesis of new macrobicyclic aza-ligands starting from “trans”dioxocyclam as diprotected macrocycle
1997
Abstract A rapid and convenient synthesis of two small aza-cryptands containing a 1,4,8,11-tetraazacyclotetradecane backbone is reported. This strategy can be applied to the preparation of many other aza-cages by varying the nature of the cross linker. Moreover, the two remaining secondary amine sites may allow the functionalization of these ligands or their grafting on a polymer.
Hydrophobicity of Ionizable Compounds. A Theoretical Study and Measurements of Diuretic Octanol−Water Partition Coefficients by Countercurrent Chroma…
1999
Countercurrent chromatography was used to determine the octanol−water partition coefficients (Po/w) of 23 diuretic drugs. The measured Po/w values ranged over 4 orders of magnitude from 0.05 to 550 (−1.3 < log Po/w < +2.7). All the compounds, except spironolactone, were ionizable. The Po/w values were strongly depending on the aqueous-phase pH. A theoretical model linking these values with the pH was derived for four cases: (i) molecular acid−anionic base, (ii) cationic acid−molecular base, (iii) biprotic systems with two acidic or basic groups showing the same charge sign, and (iv) biprotic systems with ionizable groups showing different charges with special attention to the amino acid ca…
Fluorescence enhancement of amine-capped CdSe/ZnS quantum dots by thiol addition
2011
The present communication reports that while addition of alkyl thiols drastically reduces the fluorescence of CdSe core quantum dots, it actually enhances the emission properties of already highly fluorescent amine-capped CdSe/ZnS core-shell quantum dots.
Binding properties of mono-(6-deoxy-6-amino)-β-cyclodextrin towards p-nitroaniline derivatives: a polarimetric study
2009
Abstract Polarimetry was used in order to investigate the formation of supramolecular complexes between mono-6-amino-β-cyclodextrin and various p-nitroaniline derivatives at two different pH values. Comparison with the behaviour of native β-cyclodextrin gave us the opportunity to consider the effect exerted by the presence of charged groups, having different solvation requirements, on the binding equilibrium. Data offer some support to the hypothesis of ‘dynamic co-inclusion’ of solvent molecules within the host–guest complex.
Multidentate Polysarcosine-Based Ligands for Water-Soluble Quantum Dots
2016
We describe the synthesis of heterotelechelic polysarcosine polymers and their use as multidentate ligands in the preparation of stable water-soluble quantum dots (QDs). Orthogonally functionalized polysarcosine with amine and dibenzocyclooctyl (DBCO) end groups is obtained by ring-opening polymerization of N-methylglycine N-carboxyanhydride with DBCO amine as initiator. In a first postpolymerization modification step, the future biological activity of the polymeric ligands is adjusted by modification of the amine terminus. Then, in a second postpolymerization modification step, azide functionalized di- and tridentate anchor compounds are introduced to the DBCO terminus of the polysarcosine…