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481.
Ludmila C. Fidale Constance Ißbrücker Priscilla L. Silva Camila M. Lucheti Thomas Heinze Omar A. El Seoud 《Cellulose (London, England)》2010,17(5):937-951
Although cellulose acetates, CAs, are extensively employed there is scant information about the systematic dependence of their properties on their degree of substitution, DS; this is the subject of the present work. Nine CAs samples, DS from
0.83 to 3.0 were synthesized; their films were prepared. The following solvatochromic probes have been employed in order to
determine the empirical polarity, E
T(33); “acidity, α”; “basicity, β”, and “dipolarity/polarizability, π*” of the casted films: 2,6-dichloro-4-(2,4,6-triphenyl-pyridinium-1-yl)
phenolate, WB; 4-nitroaniline; 4-nitroanisole; 4-nitro-N,N-dimethylaniline; 2,6-diphenyl-4-(2,4,6-triphenyl-pyridinium-1-yl)phenolate, RB. Additionally, two systems, ethanol plus ethyl
acetate (EtOH–EtAc), and cellulose plus cellulose triacetate, CTA, were employed as models for CAs of different DS. Regarding
the model systems, the following was observed: (i) For EtOH–EtAc, the dependence of all solvatochromic parameters on the “equivalent-DS”
of the binary mixture was non-linear because of preferential solvation; (ii) The dependence of E
T(33) on equivalent DS of the cellulose–CTA films is linear, but the slope is smaller than that of the corresponding plot for
CAs. This is attributed to the more efficient hydrogen bonding in the model system, a conclusion corroborated by IR measurements.
The dependence of solvatochromic parameters of CAs on their DS is described by the simple equations; a consequence of the
substitution of the OH by the ester group. The thermal properties of bulk CAs samples were investigated by DSC and TGA; their
dependence on DS is described by simple equations. The relevance of these data to the processing and applications of CAs is
briefly discussed. 相似文献
482.
Chou TY Chi Y Huang SF Liu CS Carty AJ Scoles L Udachin KA 《Inorganic chemistry》2003,42(19):6041-6049
The syntheses of two distinctive types of indium complex derived from trimethylindium (InMe(3)) are reported. The first kind has a generalized structural formula [InMe(2)(amak)](2), where (amak)H is an abbreviation for a series of chelating amino alcohol ligands HOC(CF(3))(2)CH(2)NHR, R = (CH(2))(2)OMe (1), Me (2), and Bu(t) (3), as well as HOC(CF(3))(2)CH(2)NMe(2) (4); while the second type of complex is illustrated by [InMe(2)(keim)] (5), for which (keim)H is a tridentate ketoimine ligand of structural formula O=C(CF(3))CH(2)C(CF(3))=NCH(2)CH(2)NMe(2). The solid-state structures of 2 and 5 were determined using single crystal X-ray diffraction studies. For the aminoalkoxide complexes 2-4, the existence of dimeric In(2)O(2) core structures in the solid state has been established with the amino fragment located trans to the alkoxide ligands, in a molecular arrangement which is in contrast to the distorted, trigonal bipyramidal geometry observed for the ketoiminate complex 5. Moreover, VT NMR studies of 2 revealed a rapid dimer-to-monomer equilibration and simultaneous rupture of the N-->In dative interaction, affording two interconvertible isomers related by having the N-Me substituents in either trans or cis dispositions. For complexes 2 and 5, deposition of In(2)O(3) thin films was successfully conducted at temperatures 400-500 degrees C, using O(2) as the carrier gas to induce indium oxide deposition and to suppress carbon impurity present in the thin film. Scanning electron micrographs (SEMs) revealed the surface morphologies. The atomic composition of these films was examined by both X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering (RBS) methods, while X-ray diffraction studies (XRD) confirmed the formation of a preferred orientation along the (222) planes. 相似文献
483.
Svetlana N. Arbuzova Nina I. Ivanova Ludmila I. Larina Grigorii G. Alexandrov Boris A. Trofimov 《Journal of organometallic chemistry》2011,696(10):2053-5732
New pyridine-phosphine chalcogenide ligands, tris[2-(2-pyridyl)ethyl]phosphine sulfide 1a and tris[2-(2-pyridyl)ethyl]phosphine selenide 1b, react with zinc(II) and cadmium(II) chlorides in EtOH at room temperature to afford complexes of compositions 2ZnCl2·2L (2, L = 1a) and 3CdCl2·2L (3a,b, L = 1a,b) in high yields. The solid-state structure of complexes 2, 3 has been proved by X-ray analysis data. Complex 2 is a centrosymmetric dimer, where two atoms of zinc are bonded by two bridging pyridine-phosphine sulfide ligands through N atoms. Complexes 3a,b exist as polymeric chains with each bridging ligand acting as a chelate N,S- or N,Se-donor to one cadmium(II) center and as a pyridine N-donor to the next cadmium(II) center. 相似文献
484.
Vadim V. Popov Stanislav A. Amelichev Ivan S. Bushmarinov Lidia S. Konstantinova Konstantin A. Lyssenko Ludmila V. Mikhalchenko Valentin V. Novikov Vadim P. Gultyai Oleg A. Rakitin 《Tetrahedron》2013
The synthesis of [1,3]dithiolo[4,5-d]dithiazolium salts from readily available zinc chelate has been developed. Chlorination of 2-oxo and 2-(dicyanomethylene) (2-oxo-1,3-dithiole-4,5-diyl) diethanethioates with SO2Cl2 followed by condensation with Me3SiN3 produced 1,2,3-dithiazolium chlorides. The structure of 5-(dicyanomethylene)[1,3]dithiolo[4,5-d][1,3,2]dithiazol-1-ium tetrafluoroborate was confirmed by powder X-ray diffraction, and its chemical bonding pattern as well as charge transfer were studied within the QTAIM framework applied to the results of plane wave DFT periodic calculations. Reduction with triphenylantimony and electrochemical reduction of [1,3]dithiolo[4,5-d]dithiazolium salts by cyclic voltammetry, chronoamperometry, and microelectrolysis at a controlled potential on a platinum electrode in acetonitrile revealed the formation of [1,3]dithiolo[4,5-d]dithiazolyl radicals, which were characterized by EPR spectroscopy. 相似文献
485.
Ludmila Hradilová Martin Grepl Jan Hlaváč Antonín Lyčka Pavel Hradil 《Journal of heterocyclic chemistry》2013,50(3):528-533
Propargyl anthranilate, a simple and less studied molecule with several reactive sites, is widely applicable in organic synthesis. An optimized synthesis of this compound and its derivatives and the preparation of azide derivatives are described. The optimized process of the known intramolecular cyclization is described, and the unknown intermolecular cyclizations of these azido derivatives and formation of a macrocycle are discussed. 相似文献
486.
Ksenia V. Zherikova Natalia B. Morozova Ludmila N. Zelenina S. V. Sysoev Tamara P. Chusova I. K. Igumenov 《Journal of Thermal Analysis and Calorimetry》2008,92(3):729-734
Five volatile hafnium(IV) and zirconium(IV) β-diketonates: hafnium(IV) acetylacetonate, hafnium(IV) trifluoroacetylacetonate,
hafnium(IV) pivaloyltrifluoroacetonate, hafnium(IV) 2,2,6,6-tetramethylheptane-3,5-dionate and zirconium(IV) 2,2,6,6-tetramethylheptane-3,5-dionate
were obtained, purified and identified. Thermal behavior of solid compounds was investigated by thermogravimetry (TG) and
differential scanning calorimetry (DSC) in helium atmosphere and in vacuum. DSC method was also used for definition of thermodynamic
characteristics of melting processes. Using the static method with quartz membrane zero-manometer and the flow method the
temperature dependencies of saturated vapor pressure for hafnium(IV) complexes was obtained. The standard thermodynamic characteristics
ΔH
T0 and ΔS
T0 of sublimation and evaporation processes were calculated from the temperature dependences of saturated vapor pressure. 相似文献
487.
Andrey A. Prishchenko Mikhail V. Livantsov Olga P. Novikova Ludmila I. Livantsova Elena R. Milaeva 《Heteroatom Chemistry》2008,19(5):490-494
Convenient procedures for the synthesis of 2,6‐di‐tert‐butyl‐4‐methylphenol (ionol) mono‐, di‐, and triphosphorus derivatives, starting from the readily accessible 3,5‐di‐tert‐butyl‐4‐hydroxybenzaldehyde, are proposed, and some properties of the obtained compounds are presented. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:490–494, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20458 相似文献
488.
Zusammenfassung Die Grundlagen der direkt-potentiometrischen Konzentrationsbestimmung von Anionen und Kationen werden beschrieben, für die keine ionensensitiven Elektroden bekannt sind. Es wird die Konzentrationsabnahme eines Hilfsions gemessen, das mit dem analytisch zu bestimmenden Ion einen stabilen Komplex bildet.Ausführliche Angaben werden zur Bestimmung von Al3+ mit F– als Hilfsion und von Ni2+ mit CN– als Hilfsion gemacht. Auf die prinzipiellen Möglichkeiten einer Bestimmung von Fe2+, Fe3+, Au+, Hg2+, Th4+, Zr4+, UO2
2+, SCN– und S2O3
2– wird eingegangen.
Direct-potentiometric determinations with ion-sensitive electrodes using complexing auxiliary reactions
The basic principles of the direct-potentiometric determination of several cations and anions are discussed, for which no ion-sensitive electrode is available. The decrease in concentration of an auxiliary ion is measured which forms stable complexes with the ion to be determined. Detailed information is given on the determination of Al3+ with F– as auxiliary ion and of Ni2+ with CN– as auxiliary ion. An outlook is presented on the possible determinations of Fe2+, Fe3+, Au+, Hg2+, Th4+, Zr4+, UO2 2+, SCN– and S2O3 2–.相似文献
489.
Alexander P. Kuznetsov Sergey P. Kuznetsov Erik Mosekilde Ludmila V. Turukina 《Physica A》2001,300(3-4)
We discuss the so-called tricritical points at the border of the period-doubling transition to chaos and examine to what extent the associated universality applies to 2D dissipative maps. As a concrete example, the Ikeda map is studied together with its 1D analog. For the approximate 1D map, the tricritical points appear as the terminal points of Feigenbaum's critical curves in the parameter plane. For the 2D map the same type of critical behavior does not occur in a rigorous sense. It may be observed as a kind of intermediate asymptotics, however, when one considers a finite number of period doublings. We refer to the associated points in the parameter plane as pseudo-tricritical. For the Ikeda map, we present estimates of the number of period doublings, after which the departure from the tricritical universality becomes essential. 相似文献
490.