bluuebunny/crossref_metadata_2025_split huggingface dataset:
Arsenite retention properties of water‐soluble metal–polymers
Authors: Rivas Bernabé L. , Aguirre María del Carmen 
Published: July 2007

AbstractThe properties of water‐soluble metal–polymers to retain As(III) from aqueous solution are investigated. Poly(acrylic acid)s with different tin contents are prepared. Amounts of 3, 5, 10, and 20 wt % of tin are added to the polymer. The metal compositions are evaluated by thermogravimetry (TG‐DSC) and atomic absorption spectroscopy. Structural properties are analyzed by infrared and 1H nuclear magnetic resonance spectroscopy, and X‐ray diffraction. Additionally, specific surface area was measured using CO2 as adsorbate. Arsenic retention properties are studied using the liquid‐phase polymer‐based retention (LPR) technique. The polymers can bind arsenic species from an aqueous solution in the pH range 4–8. The studies show that the retention capacity is a function of tin content and polymer concentration. At pH 8, the following mol ratios poly(AA)‐Sn : As(III) are analyzed: 600 : 1, 400 : 1, 200 : 1, 100 : 1, and 20 : 1. The highest retention, 80%, is obtained with poly(AA)‐Sn at 10 and 20 wt % of tin at mole ratios 400 : 1, and at nearly to 20 : 1 or 40 : 1 Sn‐As(III). The highest retention is observed at pH 8 and 4. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Synthesis of novel amino(alkylamino)deoxychitosans and those thiol‐derivatives and the chemisorption behaviors of an acid dye and Hg2+ ion onto the resulting polymers
Authors: Shimizu Yoshiaki , Akiyama Kenji , Saito Yoshihiro , Nakamura Takeo 
Published: July 2007

AbstractIntroducing an additional functionality to chitosan, novel chitosan‐based materials were synthesized. The reactions of tosylchitosan with ammonia, ethylenediamine, and hexamethylenediamine have been studied, and the chemisorption behavior of a typical acid dye (CI Acid Orange 7) onto the resulting polymers has been evaluated. Thiol groups were introduced to the above chitosan derivatives having additional amino group at the C6 position, and the chemisorption behavior of Hg2+ ion onto the resulting polymers was measured and compared with that of N‐thioacetylchitosan. The successful synthetic reaction was demonstrated by the infrared spectroscopic measurements. It has been confirmed that the abilities of the chitosan derivatives with additional amino groups to the chemisorption of an acid dye were significantly high, and that the saturation value of the chemisorption amount of CI Acid Orange 7 toward one of 2′‐aminoethylaminodeoxychitosans was significantly high as 6.16 mol/kg. The results also showed that the saturation amounts of Hg2+ ion chemisorption were larger with the increase in the thiol group content of the chitosan derivatives with the thiol groups. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Kinetics of isothermal crystallization and subsequent melting behavior of PTT/PA12 blend
Authors: Asadinezhad A. , Jafari S. H. , Khonakdar H. A. , Böhme F. , Hässler R. , Häussler L. 
Published: July 2007

AbstractThe kinetics of isothermal crystallization along with subsequent melting behavior of melt‐mixed immiscible binary blends of poly(trimethylene terephthalate) (PTT) and polyamide‐12 (PA12) were investigated by means of differential scanning calorimetry. Three macrokinetic models of Avrami, Tobin, and Malkin were used which could adequately describe isothermal crystallization kinetics of the blends as well as the neat components. However, the commonly used Avrami model provided more consistent data for the system of interest. Based on the half‐time of crystallization, one could conclude that PTT crystallizes more rapidly than PA12. The kinetic parameters suggested that blending had a distinct influence on reducing the rate of isothermal crystallization particularly at medium degrees of undercooling. From reciprocal crystallization half‐time, it was concluded that over the temperature range covered; the samples crystallized inside the nucleation‐controlled region. The secondary nucleation mechanism generally prevailed in the PA12 isothermal crystallization whereas in PTT, the primary crystallization mechanism dominated. With respect to the position of melt transitions, blending was proven to exert only small effects, however, it reduced the crystallinity of both constituents particularly that of PA12 significantly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Effect of morphology on the electric conductivity of binary polymer blends filled with carbon black
Authors: Xu Zhongbin , Zhao Chao , Gu Aijuan , Fang Zhengping , Tong Lifang 
Published: July 2007

AbstractSeveral carbon black (CB)‐filled binary polymer blends were prepared in Haake rheometer. Distribution states of CB and effect of morphology on the electric conductivity of different ternary composites were investigated. Under our experimental condition CB particles located preferentially at the interface between polymethyl methacrylate (PMMA) and polypropylene (PP) in PMMA/PP/CB composites, in high‐density polyethylene (HDPE) phase in PP/HDPE/CB composites, and in Nylon6 (PA6) phase in polystyrene (PS)/PA6/CB, PP/PA6/CB, PMMA/PA6/CB, and polyacrylonitrile (PAN)/PA6/CB composites; the ternary composites in which CB particles locate at the interface of two polymer components have the highest electric conductivity when the mass ratio of the two polymers is near to 1 : 1. The ternary composites in which CB particles located preferentially in one polymer have the highest electric conductivity usually when the amount of the polymer component having CB particles is comparatively less than the amount of the polymer component not having CB particles; if the formulations of PS/PA6/CB, PP/PA6/CB, and PMMA/PA6/CB composites equaled and PA6/CB in them is in dispersed phase, PS/PA6/CB composites have the highest electric conductivity and PP/PA6/CB composites have the lowest electric conductivity; suitable amount of PS or PAN in PA6/CB composites increase the electric conductivity due in the formation of a parallel electrocircuit for electrons to transmit. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Decomposition of a Lignin Model Compound under Hydrothermal Conditions
Authors: Wahyudiono  , Kanetake T. , Sasaki M. , Goto M. 
Published: July 2007

AbstractLignin, which is the second most abundant polymeric aromatic organic substance in wood biomass after cellulose, and contains many oxygen‐based functional groups, has been proposed as an alternative source of chemical compounds. Guaiacol, a model compound for lignin, was reacted in supercritical water using a batch‐type reactor at temperatures of 653–673 K and various pressures under an argon atmosphere. The effects of temperature and reaction time at the same pressure were combined into a single severity parameter that was used to monitor the decomposition of guaiacol to its derived compounds. The main products in aqueous solution were catechol, phenol, and o‐cresol. The amounts present approached 40.73 wt %, 14.18 wt %, and 4.45 wt %, respectively. With an increase in the reaction time at the same conditions, the amount of guaiacol decreased and the quantity of derived compounds of guaiacol increased. Based on the experimental results, a reaction mechanism for the decomposition of guaiacol was proposed. The process investigated in this study may form the basis for an efficient method of wood biomass decomposition.
Application of Interference Microscopy and IR Microscopy for Characterizing and Investigating Mass Transport in Nanoporous Materials
Authors: Heinke L. , Chmelik C. , Kortunov P. , Ruthven D. M. , Shah D. B. , Vasenkov S. , Kärger J. 
Published: July 2007

AbstractThe application of interference microscopy has provided an important breakthrough in the study of the transport of guest molecules in nanoporous materials, making it possible to observe the transient intracrystalline concentration profiles resulting from a well‐defined change (usually a step) in the ambient gas pressure. This approach was used to study adsorption and desorption kinetics in several zeolite systems. The advantages of this technique, especially when combined with infrared absorption measurements, are illustrated by experimental results obtained in a study of the methanol‐ferrierite system.
Study of Ethylene Polymerization Under Single Liquid Phase and Vapor‐Liquid Phase Conditions in a Continuous‐Flow Tubular Reactor
Authors: Beigzadeh D. , Nielsen C. A. 
Published: July 2007

AbstractThe feasibility of using continuous‐flow tubular reactors (CFTR) as an efficient research tool for polymerization reactions is investigated. This is a continuation of the extensive effort that had been made at Dow in recent years to set up and employ an electro‐thermal microreactor (an ohmically‐heated CFTR), which resulted in several internal and external publications and a US Patent. The main focus of this work is to investigate the effect of operating conditions and flow composition, mainly the number of existing phases, on the molecular weight of the polymer. A series of polymerization experiments were performed in single‐phase (liquid) and two‐phase (vapor‐liquid) flow regimes. In single‐phase polymerization, the ethylene concentration falls continuously along the length of the reactor. This will have a significant effect on the kinetics of polymerization, particularly the molecular weight of the produced polymer. A key advantage of operating in the two‐phase region is that an almost constant ethylene concentration is maintained along the length of the reactor. In effect, the vapor phase serves as a reservoir that replenishes the ethylene consumed in the liquid phase by polymerization. The molecular weight data show that this assumption is valid provided that the rate of mass transfer is significantly higher than the rate of the polymerization reaction.
Enhancement of Methanol Production in a Membrane Dual‐Type Reactor
Authors: Rahimpour M. R. , Lotfinejad M. 
Published: July 2007

AbstractIn this study, a dynamic model for a membrane dual‐type methanol reactor was developed in the presence of long term catalyst deactivation. The proposed model is used to compare the performance of a membrane dual‐type methanol reactor with a conventional dual‐type methanol reactor. A conventional dual‐type methanol reactor is a shell and tube heat exchanger reactor in which the first reactor is cooled with cooling water and the second one is cooled with synthesis gas. In a membrane dual‐type reactor, the wall of the tubes in the gas‐cooled conventional reactor is covered with a palladium‐silver membrane, which is only permeable to hydrogen. Hydrogen can penetrate from the feed synthesis gas side into the reaction side due to the hydrogen partial pressure driving force. Hydrogen permeation through the membrane shifts the reaction towards the product side according to the thermodynamic equilibrium. The proposed dynamic model was validated against measured daily process data of a methanol plant recorded for a period of four years and a good agreement was achieved. The simulation results show that there is a favorable profile of temperature and activity of the membrane dual‐type reactor relative to single and conventional dual‐type reactor systems. Therefore, the performance of methanol reactor systems improves when a membrane is used in a conventional dual‐type methanol reactor.
In3Ti2Br9: Jahn‐Teller Unstable Indium(I) and Antiferromagnetically Coupled Titanium(III) Atoms
Authors: Dronskowski Richard 
Published: July 2007

AbstractDark green crystals of In3Ti2Br9 have been synthesized from elemental Ti and molten InBr3 at 450°C. The X‐ray diffractional characterization by means of single‐crystal and powder Rietveld refinement reveals a hexagonal crystal structure (a = 738.2(2), c = 1813.9(3) pm; P63/mmc, Z = 2) of Cs3Cr2Cl9 type, containing Ti2Br3−9 dimers and univalent indium cations. Self‐consistent, semiempirical band structure calculations show the structural distortions of the two monovalent indium cations to arise from a second‐order Jahn‐Teller instability. The new compound's magnetic susceptibility and microscopic antiferromagnetic exchange are analyzed by using a Bleaney‐Bowers ansatz.
Novel Metastable Structures of WO3, MoO3 and W1‐xMoxO3 Obtained by the Deintercalation of Layered Amine Adducts
Authors: Ayyappan S. , Subbanna G. N. , Rao C. N. R. 
Published: July 2007

AbstractDeintercalation of amines from the layered amine adducts of WO3, MoO3 and W1‐xMoxO3 has been employed as a soft chemical route to produce unusual metastable structures of the oxides. After the adducts of WO3, MoO3 and W1–xMoxO3 (x = 0.25, 0.5, 0.75) with amines such as triethylamine (TEA), pyridine, n‐butylamine and n‐octylamine had been characterized, deintercalation was carried out thermally as well as by acid leaching. Thermal deintercalation yielded novel metastable structures of WO3 and MoO3 that were significantly different from the stable forms, which contain distorted metal‐oxygen octahedra. Thus, ReO3‐type cubic WO3 was obtained by the thermal deintercalation of WO3 · 0.5 TEA. Acid leaching of the amines gave metastable phases of WO3, MoO3 and W1‐xMoxO3, which were different from those obtained thermally. All the metastable phases transformed to the corresponding stable forms at higher temperatures.
The Reaction of H2S with SO2: Molecular Structures, Energies, and Vibrational Data of Seven Isomeric Forms of H2S3O
Authors: Drozdova Yana , Steudel Ralf 
Published: July 2007

AbstractHigh‐level ab initio MO calculations (MP2/6‐311G**//MP2/6‐311G**) on 16 isomeric forms of H2S3O (including rotamers) have been performed. The nonhelical hydroxotrisulfane HOSSSH 1a (motif + + −) is the most stable isomer, while the chains with motifs + + + and + − + are less stable by 1.7 and 3.7 kJ mol−1, respectively. The other isomers of H2S3O increase in energy in the order HSS(O)SH < HOS(S)SH < HSOSSH < HS(O)SSH < HS(S)SOH < HS(S)OSH. The trisulfane‐2‐oxide HSS(O)SH 2a (symmetry C1) is less stable than 1 a by 67 kJ mol−1. These molecules may be formed from H2S and SO2 via H2S2O2 by condensation with H2S. The calculated reaction energies support the view that H2S3O is a key intermediate in the room‐temperature reaction of H2S and SO2 resulting in the formation of lower oxoacids of sulfur and finally in sulfane oxides.
Correlations Between Structure, Magnetism, and Polymerization Activity of Paramagnetic Benzylchromium Complexes
Authors: Bhandari Gautam , Rheingold Arnold L. , Theopold Klaus H. 
Published: July 2007

AbstractReaction of [{Cp*Cr(μ‐Cl)}2] with benzyllithium yielded [{Cp*Cr‐(μ‐Bz)}2] (1), a CrII alkyl complex with bridging benzyl groups and a CrCr bond, which rearranged at room temperature to [Cp*Cr(η1‐Bz)(μ‐η3:η6‐Bz)CrCp*] (2), a mixed valent (CrI/CrIII) complex with a benzyl ligand coordinating as an η6‐arene ligand to one chromium and as an η3‐allyl ligand to the other one. Upon heating, 2 reductively eliminated bibenzyl and yielded [(Cp*Cr)2(μ‐η6:η6‐Bz‐Bz)] (3), in which two 17‐electron sandwich complexes are linked by an ethano bridge. The crystal structures of 2 and 3 have been determined. Magnetic susceptibility and saturation magnetization measurements showed 2 to be ferromagnetically coupled (ground state S = 2, J = + 23(1) cm−1). Of the three isomers, only 2 catalyzed the polymerization of ethylene, presumably because it contains a CrIII alkyl.
Asymmetric syn‐Selective Michael Addition of Enolates to Chiral 8‐Phenylmenthyloxy Vinyl Chromium Carbene Complexes
Authors: Barluenga José , Montserrat Javier M. , Flórez Josefa , Garcia‐Granda Santiago , Martin Eduardo 
Published: July 2007

AbstractMichael addition reactions of ketone and ester lithium enolates to optically active Fischer vinylcarbene complexes derived from (‐)‐8‐phenylmenthol take place with high syn selectivity and high levels of asymmetric induction. The initial Michael adducts can be further elaborated through diastereoselective addition of organometallic reagents to ketones and aldol reactions. Removal of the metal fragment and chiral auxiliary group leads to cyclic enol ethers with three or five contiguous stereogenic centers and of high enantiomeric purity.
Diastereo‐ and Enantioselective Synthesis of L‐threo‐ and D‐erythro‐Sphingosine
Authors: Enders Dieter , Whitehouse Darren L. , Runsink Jan 
Published: July 2007

AbstractL‐threo‐sphingosine and its D‐erythro isomer (1) are subunits of many glycosphingolipids, gangliosides and ceramides. This paper describes the highly diastereo‐ and enantioselective synthesis of both isomers (de, ee > 98%). The key steps in the synthesis are the aldol reaction of the SAMP hydrazone (S)‐2 with racemic α‐phenylselenylpentadecanal 3, the diastereoselective triacetoxyborohydride reduction of ketone 5 and exclusive (E) CC double bond formation in the elimination of hydroxyl and selenyl moieties promoted by methanesulfonyl chloride. Mesylate 8 was then readily converted via the 1,3‐O‐acetonide‐protected azidosphingosine 9 to L‐threo‐sphingosine. Conversion to the known 1‐O,2‐N‐diacetyl‐protected sphingosine 13 with subsequent Mitsunobu inversion of the C3OH centre afforded the D‐erythro‐sphingosine epimer.
Phase Relationships in the N2O3/N2O4 System and Crystal Structures of N2O3
Authors: Horakh Jörg , Borrmann Horst , Simon Arndt 
Published: July 2007

AbstractMixtures of N2O3 and N2O4 have been prepared from measured volumes of NO and O2. Phase relationships in the system N2O3/N2O4, which depend on the composition of the samples and on the temperature, were studied by the Guinier technique and differential thermal analysis. Single crystals of phases A and B of N2O3 were grown in situ on a diffractometer and studied at temperatures between −107 and −170°C by X‐ray diffraction. The structure analysis of A‐N2O3 (tetragonal, space group I41/a, T = −170°C, a = 1625.57 (16), c = 880.49(13) pm, Z = 32, R1 = 0.051 for 1030 unique reflections) is hampered by twinning and additional disorder of one of two crystallographically independent molecules. B‐N2O3 is nicely ordered with one molecule in the asymmetric unit (orthorhombic, space group P212121, T = −160°C, a = 506.86(4), b = 647.96(5), c = 863.26(6) pm, Z = 4, R1 = 0.023 for 1352 unique reflections). The most interesting features of the N2O3 molecule are its planarity and the extraordinarily long NN bond (189.0(1) pm).
Biologically Induced Reduction in Symmetry: A Study of Crystal Texture of Calcitic Sponge Spicules
Authors: Aizenberg Joanna , Hanson Jonathan , Koetzle Thomas F. , Leiserowitz Leslie , Weiner Stephen , Addadi Lia 
Published: July 2007

AbstractOrganisms can exert a remarkable degree of control over crystal growth. One way of achieving this is by the adsorption of specialized macromolecules on specific planes of the growing crystals. With continued growth of the crystal, the macromolecules are incorporated inside the crystal bulk. Their presence does not change the crystal structure, but creates discontinuities in the perfect lattice. Here we study in detail three unusual cases of reduction in symmetry at the level of crystal domain shapes, induced by this controlled intercalation. We examined sponge spicules, which are single crystals of Mg‐bearing calcite. They were specifically chosen for this study, because their morphologies do not reflect the hexagonal symmetry of calcite. Their crystal textures (coherence lengths and angular spreads) were characterized by high‐resolution X‐ray diffraction with well‐collimated synchrotron radiation. The results are compared to analogous studies of synthetic calcite and Mg‐bearing calcite. In all the selected spicules reduction in symmetry is observed in the coherence lengths among symmetry‐related crystallographic directions. The reconstructed shapes of the domains of perfect structure closely match the specific spicule morphologies. The synthetic crystals show no such reduction in symmetry. Although the manner by which such exquisite control is achieved is not known, we envisage it involving a combination of oriented nucleation with either physical or stereochemically driven adsorption.
Weak Interactions in Crystals: 4,4′‐Di(tert‐butyl)‐N‐N′‐bipyridinium Diperchlorate—A Biphenyl Analogue with Perpendicular Pyridine Rings
Authors: Bock Hans , Nick Sabine , Näther Christian , Bensch Wolfgang 
Published: July 2007

AbstractOxidation of substituted N‐aminopyridinium compounds yields bipyridinium salts. After anion exchange Br− → CIO, it was possible to grow single crystals from the 4,4′‐di(tert‐butyl) derivative. The structure determined at 100 K shows a dihedral angle of 84° between the molecular halves connected by a shortened NN bond of 143 pm in length. This result is contrary to that expected from the isoelectronic correspondence 〉CC〈↔〉NN〈, which would suggest planarity, as has been observed experimentally both in solid biphenyl, and in tetraalkylhydrazine dications and radical cations. Lattice packing analysis, however, reveals the presence of hydrogen bonds C(H)…O between the phenyl rings and the perchlorate anions. AM 1 enthalpy hypersurface calculations for the isoelectronic series H5C5X–YC5H5 (X–Y = CC, +NC, +NN+, −BN+, BC, and BB−) predict single‐minimum potentials for both the dication 〉NN〈 as well as the dianion 〉BB〈 with the molecular halves twisted perpendicular to each other. In detailed model calculations, counteracting effects of π electron density delocalization vs. H/H repulsion of the ortho ring hydrogens adjacent to the central bond seem to dictate the delicate balance of the biphenyl twisting. For further experimental confirmation, the structure of the isosteric molecule 4,4′‐di(tert‐butyl)biphenyl has been determined: in contrast to the unsubstituted π hydrocarbon with a latticeenforced dihedral angle of 0°, close to the calculated value, the two molecular halves are twisted by 40°—as in biphenyl in the gas phase.
Transfer Hydrogenation of Nitro‐, Nitroso‐ and Azoarenes by Homolytic Retrodisproportionation
Authors: Coellen Michael , Rüchardt Christoph 
Published: July 2007

AbstractNitro‐, nitroso‐ and azobenzene are reduced almost quantitatively to aniline when heated to 230–300°C with 9,10‐dihydroanthracene (DHA), xanthene or tetralin. From the effect of polar substituents and polar solvents on the reactivity and from the isotope effect kH/kD ≈︁ 2.4 (280°C), a hydrogen‐atom transfer from the H donor to the acceptor (retrodisproportionation) is proposed as the rate‐determining step. The lower reactivity of xanthene compared with 9,10‐dihydroanthracene eliminates the possibility of a rate‐determining hydride transfer. The observation of an intense ESR signal of 9‐xanthyl radicals during the reaction in diphenyl ether and the typical products support the proposed homolytic mechanism.
Bimolecular Gas‐Phase Reactions of d‐Block Transition‐Metal Cations With Dimethyl Peroxide: Trends Across the Periodic Table
Authors: Wesendrup Ralf , Schalley Christoph A. , Schröder Detlef , Schwarz Helmut 
Published: July 2007

AbstractThe bimolecular gas‐phase reactions of d‐block transition‐metal cations M+ with dimethyl peroxide were screened by means of Fourier transform ion cyclotron resonance mass spectrometry. The rich chemistry can be classified into four types of reactions: i) Oxygen‐atom transfer to generate MO+, ii) elimination of radicals, mostly CH3O˙, iii) intramolecular redox reaction of dimethyl peroxide to form CH3OH, CH2O and CO, and iv) charge transfer from the metal cation to produce CH3OOCH3+. Some general trends became apparent from this study. For example, the “early” transition metals almost exclusively induce oxygen transfer to generate MO+, in line with the notoriously high oxophilicities of these metals, and electron transfer is only observed for Zn+ and Hg+. Both the radical loss and the disproportionation reaction emerge from a rovibrationally highly excited insertion intermediate (CH3O)2M+, and for the first‐row metals the branching ratio of the competing processes seems to be affected by the M+OR bond strengths as well as the electronic groundstate configurations of M+. For the 4d and 5d cations Ru+Ag+ and Pt+Au+, respectively, products resulting from intramolecular redox reactions dominate; this probably reflects the higher propensity of these metal ions to facilitate β‐hydrogen atom shifts.