Search results for "ether"
showing 10 items of 986 documents
Continuous polymer fractionation of poly(methyl vinyl ether) and a new Kuhn-Mark-Houwink relation
1995
Continuous polymer fractionation (CPF) — a new large-scale method — was applied to the technical poly(methyl vinyl ether) (PVME) using toluence as solvent and petroleum ether as non-solvent. Two different devices served as fractionation apparatus, namely a column packed with glass beads and a set of mixer-settler extractors. Advantages and draw-backs of these devices are discussed. The experiments yielded numerous PVME fractions, varying in molar mass from 22 to 87 kg/mol and in molecular non-uniformity U = (M¯w/Mn) – 1 from 0,25 to 0,41 according to gel-permeation chromatography as compared with ca. U = 1,30 for the starting material. The following Kuhn-Mark-Houwink relation was establishe…
Toward an Understanding of the Catalytic Role of Hydrogen-Bond Donor Solvents in the Hetero-Diels−Alder Reaction between Acetone and Butadiene Deriva…
2006
A detailed theoretical investigation of the catalytic role of hydrogen-bond- (HB-) donor molecules (water, methanol, chloroform, dichloromethane, and chloromethane) in the hetero-Diels-Alder reaction between acetone and N,N-dimethyl-1-amino-3-methoxy-1,3-butadiene is presented. This work extends a previous study (Domingo, L. R.; Andres, J. J. Org. Chem. 2003, 68, 8662) in which the importance of weak HB-donor solvents to catalyze more effectively than solvents with a higher dielectric constant but no HB-donor capability was analyzed. Now, based on density functional theory (DFT) at B3LYP/6-31+G(d) level calculations, different techniques for analyzing the nature of HB interaction, namely, n…
A Trinuclear Copper(II) Cryptate and Its μ3-CO3 Cascade Complex: Thermodynamics, Structural and Magnetic Properties
2011
The 2,4,6-triethylbenzene-capped hexaamine macrobicycle with pyridyl spacers (pyr) was able to coordinate three copper(II) ions within its cavity. Potentiometric studies performed at 298.2 K in MeOH/H(2)O (50:50 v/v) and at ionic strength 0.10 mol dm(-3) in KNO(3) revealed that trinuclear species predominate in solution from pH 5.0, the hydroxo complexes being the main species, which start forming at unusual very low pH values. The single-crystal X-ray determination of the trinuclear complex showed that the three copper centres have square-planar geometry, arranged in an almost equilateral triangle, and have carbonate bridging the three metal centres. The presence of carbonate resulted from…
Unusual conformations of 1,3-dialkoxythiacalix[4]arenes in the solid state
2006
The structures of three syn-1,3-dialkoxythiacalix[4]arenes with unusual conformations in the solid state are reported. The pinched cone conformation of syn-2 2 ,4 2 -dihydroxy-1 2 ,3 2 -bis-(prop-2-enyloxy)thiacalix[4]arene, C 30 H 24 O 4 S 4 , (3a), is stabilized by two intramolecular hydrogen bonds, remarkably formed from both OH groups to the same ether O atom. In syn-22,42-dihydroxy-1 5 ,2 5 ,3 5 ,4 5 -tetranitro-12,32-bis(prop-2-enyloxy)thiacalix[4]arene acetone disolvate, C 30 H 20 N 4 O 12 S 4 ·-2C 3 H 6 O, (3b1), the molecule is found in the 1,3-alternate conformation. The crystallographic C2 symmetry is due to a twofold rotation axis running through the centre of the calixarene rin…
Boolean operations mediated by an ion-pair receptor of a multi-readout molecular logic gate
2013
A heteroditopic BODIPY dye that performs all basic Boolean operations with a cation (K+) and an anion (F-) as inputs and absorption, transmission and fluorescence as outputs is described. The molecular logic gate can also act as a digital comparator between the inputs.
Helicates with Ether-Substituted Catechol Esters as Ligands
2020
European journal of organic chemistry 2020(32), 5161-5172 (2020). doi:10.1002/ejoc.202000843
A highly selective, Hg2+ triggered hydrogelation: modulation of morphology by chemical stimuli
2013
We report the first Hg(2+) selective hydrogelation by 4'-[4-(4-aminophenyl)phenyl]-2,2':6',2''-terpyridine. The gel showed remarkable response towards specific chemical agents such as benzo-18-crown-6 ether and K(+) which enabled extensive modulation of the gel morphology.
Brominated flame retardants and toxic elements in the meat and liver of red deer (Cervus elaphus), wild boar (Sus scrofa), and moose (Alces alces) fr…
2017
In order to evaluate the contamination status of terrestrial biota in Latvia, muscle and liver tissues of red deer (Cervus elaphus), wild boar (Sus scrofa), and moose (Alces alces) were analyzed for the content of polybrominated diphenyl ethers (PBDE), hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBPA), as well as cadmium and lead. The highest mean concentrations of PBDEs (46.6pgg-1 wet weight (w.w.)), cadmium (0.95mgkg-1 w.w.), and lead (0.22mgkg-1 w.w.) were observed in the tissues of moose, while the wild boar samples contained the highest levels of HBCD, with the mean concentration equal to 264pgg-1 w.w. in muscle tissues. Generally low mean concentrations of TBBPA from 0.52 t…
Liquid–liquid equilibria of the systems dipropyl ether+n-propanol+water and dipropyl ether+n-propanol+ethylene glycol at different temperatures
2007
Abstract In this work, experimental liquid–liquid equilibria (LLE) data of the dipropyl ether + n-propanol + water and dipropyl ether + n-propanol + ethylene glycol systems are presented. The LLE of both systems have been measured at 283.15 and 323.15 K. The equilibrium data presented are correlated using NRTL and UNIQUAC equations. The reliability of these models is tested by comparison with experimental results. Moreover, the solvent capabilities of water and ethylene glycol were compared, concluding that ethylene glycol is the best solvent to extract n-propanol.
CCDC 201880: Experimental Crystal Structure Determination
2007
Related Article: S.Schwarz-Barac, H.Ritter, D.Schollmeyer|2003|Macromol.Rapid Commun.|24|325|doi:10.1002/marc.200391325