Search results for "ether"

Chemometrics:  An Important Tool for the Modern Chemist, an Example from Wood-Processing Chemistry

2000

This study briefly outlines the idea of principal component analysis and cross-correlation calculations (applied chemometrics) and presents an illustrative example from wood-processing chemistry. The applicability of chemometric data analysis was demonstrated by investigating the various structural changes that take place in dissolved and degraded lignin ("kraft lignin") during laboratory-scale kraft pulping of Scots pine (Pinus sylvestris) and silver birch (Betula pendula). The structural data (31P NMR and size exclusion chromatographic data) on kraft lignin were further processed by chemometric multivariate techniques (PCA and 2DCC), confirming, for example, that the cleavage of beta-aryl…

Quantitative determination of octylphenol, nonylphenol, alkylphenol ethoxylates and alcohol ethoxylates by pressurized liquid extraction and liquid c…

2007

6 páginas, 1 figura, 2 tablas.

ChemInform Abstract: A High-Yielding Modular Access to the Lamellarins: Synthesis of Lamellarin G Trimethyl Ether (Ia), Lamellarin η (II) and Dihydro…

2014

2,2′-Oxydiacetato-bridged complexes containing Sm(III) and bivalent cations. Synthesis, structure, magnetic properties and chemical speciation

2006

Abstract Heterometallic compounds containing Sm(III), bivalent cations M (M = Cu, Ni, Co, Mn, Ca, Mg), and 2′,2′-oxydiacetate (oda) as connecting ligand have been prepared and characterized. The complexes can be formulated as [Sm 2 M 3 (oda) 6 ] · xH 2 O. The structure of [Sm 2 Cu 3 (oda) 6 (H 2 O) 6 ] shows the presence of the Sm(III) coordinated by six carboxy and three ether oxygen atoms, and the Cu(II) cation bonded to four carboxy oxygens and two molecules of water. An open 3D framework is observed, containing large hexagonal channels. At room temperature, the polynuclear complexes behave as built by magnetically isolated paramagnetic ions, but at low temperatures, very weak antiferrom…

Lanthanide bis(trifluoromethylsulfonyl)amides vs. trifluoromethylsulfonates as catalysts for Friedel–Crafts acylations

2002

Abstract The use of catalytic amounts: 1 mol% or less of perfluoroalkyl lanthanide salts as homogeneous catalysts for Friedel–Crafts acylations in non-hazardous solvents is thereafter investigated. Lanthanide bis(trifluoromethylsulfonyl)amides are better catalysts than the triflate analogues towards the acetylation of activated aromatic rings.

Neutral and cationic trimethylsilylmethyl complexes of the rare earth metals supported by a crown ether: synthesis and structural characterization

2003

The synthesis of a series of thermally robust, isolable trimethylsilylmethyl complexes of the rare earth metals stabilized by 12-crown-4 [Ln(CH2SiMe3)3(12-crown-4)] (Ln = Sc, Y, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) is reported. The crystallographically characterized yttrium and lutetium complexes [Ln(CH2SiMe3)3(12-crown-4)] exhibit facial coordination of the crown ether at the neutral lanthanide trialkyl unit. The coordination geometry can be derived from a capped octahedron. VT NMR spectroscopic studies revealed a labile coordination of the crown ether in thf solution. Reaction of the diamagnetic derivatives with triethylammonium tetraphenylborate in thf results in the clean formation of th…

Conformationally Mobile Wide Rim Carbamoylmethylphosphine Oxide (CMPO)-Calixarenes

1999

Six new calix[4]arene derivatives 2a–f have been synthesised, bearing CMPO-like functions (-NH–C(O)–CH2–P(O)Ph2) at their wide rim. They differ by their alkoxy groups at the narrow rim, comprising all possible combinations of methoxy and syn-propoxy groups including the conformationally mobile tetramethyl ether 2e and the tetrapropyl ether 2f fixed in the cone conformation. Their extraction behaviour for thorium(IV) and several lanthanides(III) from 1M HNO3 to dichloromethane has been studied and compared also to non cyclic calixarene analogues 6a–e. Surprisingly the best extraction results were found for the 1,2-dimethoxy-3,4-dipropoxy derivative 2c among the calixarenes and for the tetram…

Complexation of M3+Lanthanide Cations by Calix[4]arene-CMPO Ligands: A Molecular Dynamics Study in Methanol Solution and at a Water/Chloroform Interf…

2000

Abstract We report a molecular dynamics study on the 1:1 M3+ lanthanide (La3+, Eu3+ and Yb3+) inclusion complexes of an important extractant molecule L: a calix[4]arene-tetraalkyl ether substituted at the wide rim by four NH-C(O)-CH2-P(O)Ph2 arms. The M(NO3)3 and MCl3 complexes of L are compared in methanol solution and at a water / chloroform interface. In the different environments the coordination sphere of M3+ involves the four phosphoryl oxygens and three to four loosely bound carbonyl oxygens of the CMPO-like arms. Based on free energy simulations, we address the question of ion binding selectivity in pure liquid phases and at the liquid-liquid interface where L and the complexes are …

Titanium and zirconium complexes that contain a tridentate bis(phenolato) ligand of the [OOO]-type

2003

Abstract The oxygen-linked bis(phenol) 2-oxapropanediyl-1,3-bis(2-tert-butyl-4-methylphenol), [OOO]H2, was prepared in good yield by the condensation of 2-tert-butyl-6-hydroxymethyl-4-methylphenol at 155 °C. This bis(phenol) reacted cleanly with titanium tetrachloride to give the orange titanium dichloro complex [OOO]TiCl2 in virtually quantitative yield. The solubility in pentane indicates a monomeric structure for [OOO]TiCl2 in solution. The reaction of titanium tetra(isopropoxide) gave the di(isopropoxy) complex [OOO]Ti(OiPr)2 which also adopts a monomeric structure of C2v-symmetry in solution. The reaction of the dichloro complex [OOO]TiCl2 with benzyl Grignard reagent in diethyl ether …

Synthesis of tritium labeled (�)-1-[2(triphenylmethoxy)ethyl]-3-piperidinecarboxylic acid: a possible compound to determine the efficacy of potential…

2000

(±)-1-[2-(Triphenyl[ 3 H]methoxy)ethyl]-3-piperidinecarboxylic acid ([ 3 H]SNAP-5114) with a specific activity of 40 Ci/mmol was prepared in a two step synthesis starting from ethyl (2-(4-hydroxyphenyl)bis(4-methoxyphenyl)methoxy)-ethyl)piperidine-3-carboxylate and [ 3 H]methyliodide with subsequent hydrolysis of the resulting ester with lithium hydroxide to yield the desired [ 3 H]SNAP-5114.