Kinetics and mechanism of Yb(III) extraction and separation from Y(III) with mixtures of bis(2,4,4-trimethylpentyl)phosphinic acid and 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester

The ytterbium(III) extraction kinetics and mechanism with mixtures of bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex272) and 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (P507) dissolved in heptane have been investigated by constant interfacial cell with laminar flow. The effects of the stirring rate, temperature, extractant concentration, and pH on the extraction with mixtures of Cyanex272 and P507 have been studied. The results are compared with those of the system with Cyanex272 or P507 alone. It is concluded that the Yb(III) extraction rate is enhanced with mixtures extractant of Cyanex272 and P507 according to their values of the extraction rate constant, which is due to decreasing the activation energy of the mixtures. At the same time, the mixtures exhibits no synergistic effects for Y(III), which provides better possibilities for Yb(III) and Y(III) separations at a proper conditions than anyone alone. Moreover, thermodynamic extraction separation Yb(III) and Y(III) by the mixtures has been discussed, which agrees with kinetics results. Extraction rate equations have also been obtained, and through the approximate solutions of the flux equation, diffusion parameters and thickness of the diffusion film have been calculated.

Formation of mesophase mono-domains and micro-structures in thin films of a series of copolyethers containing both odd-numbered methylene units

The structural and morphological evolution of mono-domains in thin films has been investigated for a series of liquid crystalline (LC) copolyethers. The copolyethers studied were synthesized by the reaction of 1-(4-hydroxy-4 ' -biphenylyl)-2-(4-hydroxyl-phenyl)propane (TPP) with 1,7-dibromoheptane and 1,11-undecane at different compositions (coTPPs-7/11). In contrast to the solution-cast thin films without annealing, which exhibit the isotropic homogeneous molecular orientation, mono-domains with a homeotropic alignment were found in coTPP-7/11(5/5) after the thin films were annealed in the high-temperature columnar phase (Phi '). Similar to the nucleation process in polymer crystallization, transmission electron microscopic observations show that small mono-domains appear in the initial stage of annealing, where molecules form a uniaxial in-plane chain orientation. With increasing annealing time, the molecular orientation gradually became tilted with respect to the substrate surface, and finally, a uniaxial homeotropic molecular orientation was achieved after a prolonged annealing time. The lateral size of mono-domains was found to increase continuously with annealing time and grew into a circular shape, indicating an isotropic lateral growth scheme which implies a hexagonal molecular packing proved by the electron diffraction experiments.

Synthesis of the first mono(cyclopentadienyl)lanthanide Schiff base complex bearing C-2-symmetric tetradentate ligand: crystal structure of [(eta(5)-C5H5)Yb(mu-OC20H20N2O)](2)(mu-THF)(THF)

Reaction of YbCl3 with 3 equimolar CpNa (Cp = cyclopentadienide) in THF, followed by treatment with trans-(+/-)-N,N'-bis(salicylidene)-1,2-cyclohexanediamine led to the isolation of first mono(cyclopentadienyl) lanthanide Schiff base complex, [(eta(5)-C5H5)Yb(mu-OC20H20N2O)](2) (mu-THF)(THF) (1). The molecular structure of 1 shows that it is a dimer in which the two [(eta(5)-C5H5)Yb(mu-OC20H20N2O)] units connecting via a bridging THF oxygen and two bridging oxygen atoms from Schiff base ligands. (C) 1998 Elsevier Science S.A.

Synthesis and X-ray crystal structure of [(eta(5)-C5H5)Sm(mu-OC20H20N2O)](2)(mu-THF)(THF)(2): Mono(cyclopentadienyl)lanthanide complex bearing a C-2-symmetric tetradentate Schiff-base ligand

Cp2SmCl(THF) reacts with 0.5 equivalent disodium salts of trans-(+/-)-N,N'-bis(salicylidene)-1,2-cyclohexanediamine give the title complex [(eta(5)-C5H5)Sm(mu-OC20H20N2O)](2)(mu-THF)(THF)(2) (1). X-ray crystal determination shows that the molecule is a dimer, in which two (eta(5)C(5)H(5))Sm(mu-OC20H20N2O) units are connected via a THF oxygen and two bridging oxygen atoms of Schiff base ligands. The average Sm-C distance is 2.78(7) Angstrom, while those of Sm-O (bridging THF oxygen) and Schiff base oxygens are 2.79(3) and 2.43(4) Angstrom; respectively. (C) 1998 Elsevier Science Ltd. All rights reserved.

THE CATALYTIC ACTIVITY OF HETEROPOLY ACIDS (SALTS) AND MONO-LACUNARY HETEROPOLY TUNGSTOPHOSPHORIC COMPOUND IN THE OXIDATION OF ALCOHOLS

The catalytic activity of heteropoly compounds in the oxidation of benzyl alcohol and cyclohexa nol under phase transfer conditions has been studied. The catalytic activity of six kinds of heteropoly acids with Keggin structure will drop by the order of GeMo12 (H4GeMo12O40). PW12, PMo12, SiMo12, GeW12 and SiW12. When the three protons of H3PW12O40 Were replaced by Na+ step by step, the catalytic activity will raise gradually with the drop of acidity. The addition of base and trace amount of sulfuric acid to the reaction system resulted in an increase of catalytic activity. It was found that catalytic activity of mono-lacunary heteropoly compounds is higher than that of the primary heteropoly acids (or salts). The catalytic oxidation system of HPA-H2O2-PTC is very active in the oxidation of benzyl alcohol ana cyclohexanol, but it has little activity in the oxidation of inactive compounds such as n(or iso)-proplalcohol. n-butyl alcohol and n-hexanol. Solvent has great effect on reaction, when polar compounds such as water were used as solvent, the catalytic activity is better than that when non-polar compounds were used as solvent.

CRYSTALLINITY OF UNIFORM OLIGO(OXYETHYLENE) MONO-N-ALKYL ETHERS STUDIED BY X-RAY-DIFFRACTION AND DIFFERENTIAL SCANNING CALORIMETRY

The crystallinity of two series of uniform oligo(oxyethylene) mono-n-alkyl ethers has been investigated: alpha-alkyl,omega-hydroxyoligo(oxyethylene)s, H(CH2)n(OCH2CH2)mOH, and alpha-alkyl,omega-methoxyoligo(oxyethylene)s, H(CH2)n(OCH2CH2)mOCH3. The hydroxy-ended oligomers formed bilayer crystals, and the methoxy-ended oligomers formed monolayer crystals. The helical oxyethylene blocks were oriented normal to the layer-crystal end-group plane, whilst the trans-planar alkyl blocks were generally tilted at an angle delta = 60-degrees. The melting temperature and enthalpy of fusion were higher for hydroxy-ended oligomers than for corresponding methoxy-ended oligomers.

Highly brominated mono- and bis-phenols from the marine red alga Symphyocladia latiuscula with radical-scavenging activity

Four new highly brominated and fully substituted mono- and bis-phenols, 1-(2,3,6-tribromo-4,5-dihydroxybenzyl)pyrrolidin-2-one (1), 1,2-bis(2,3,6-tribromo-4,5-dihydroxyphenyl)ethane (2), 6-(2,3,6-tribromo-4,5-dihydroxybenzyl)-2,5-dibromo-3,4-dihydroxybenzyl methyl ether (3), and 2,3,6-tribromo-4,5-dihydroxybenzyl methyl sulfone (4), were characterized from the marine red alga Symphyocladia latiuscula. In addition, five known bromophenols, bis(2,3,6-tribromo-4,5-dihydroxyphenyl)methane (5), bis(2,3,6-tribromo-4,5-dihydroxybenzyl) ether (6), 2,3,6-tribromo-4,5-dihydroxybenzyl methyl ether (7), 2,3,6-tribromo-4,5-dihydroxymethylbenzene (8), and 2,3,6-tribromo-4,5-dihydroxybenzaldehyde (9), were also isolated and identified. The structures of these compounds were elucidated by spectroscopic methods including 1D and 2D NMR as well as by low- and high-resolution mass spectrometric analysis. Structurally, all of these compounds are highly brominated and fully substituted, and contain one or two 2,3,6-tribromo-4,5-dihydroxyphenyl unit(s) in each of the molecules. In addition, compound 4 possesses a unique sulfone structural feature. Each of the isolated compounds was evaluated for alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH) radical-scavenging activity and all were found to be potent, with IC50 values ranging from 8.1 to 24.7 mu M, compared to the known positive control butylated hydroxytoluene (BHT), with an IC50 of 81.8 mu M.

Assessing genetic identity of sporophytic offspring of the brown alga Undaria pinnatifida derived from mono-crossing of gametophyte clones by use of amplified fragment length polymorphism and microsatellite markers

The haploid stage of gametophytes of the subtidal brown alga Undaria pinnatifida can be vegetatively propagated under favorable conditions. This unique characteristic makes it possible to establish independent gametophyte cell lines that are zoospore-derived. Sporophytic offspring can be generated through hybridizing the male and female gametophytes, which are derived from different cell lines. Accumulated experiences in this and other species in Laminariales demonstrated the applicability of this novel way to breed desired strains for open-sea cultivation. Sporophytic offspring originated from mono-crossing of male and female gametophyte clones were shown to have similar morphological characteristics under identical ambient conditions. However, there has been no report to relate this similarity on molecular levels. In this report, amplified fragment length polymorphism (AFLP) and microsatellite markers were used to analyze the genetic identity of sporophytic offspring of U. pinnatifida originated from two mono-crossing lines (M1 and M2), two self-breeding lines (S1 and S2) and one wild population (W). Totally 318 AFLP loci were revealed by use of 11 primer sets, of which 4.7%, 0.3%, 17.9%, 16.4% and 36.5% were polymorphic in M1, M2, S1, S2 and W, respectively. The pairwise genetic identity among the individuals of the same line was assessed. It was shown that offspring from mono-crossing lines had a higher degree of identity (95.6-100%) than self-breeding lines (87.7-98.4%) and the wild population (81.5-92.1%). Analysis by use of six microsatellite loci also revealed a higher genetic identity among individuals of the mono-crossing line, further confirming the results of AFLP analysis. Results from this investigation support, on molecular levels, the novel way to produce and maintain strains in U. pinnatifida by use of different gametophyte cell lines.

Influencia de sete porta-enxertos mono e poliembrionicos sobre quatro cultivares de mangueira no cerrado de Brasilia-DF.

2001