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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 8 (1996), S. 397-401 
    ISSN: 0899-0042
    Keywords: chiral derivatization ; capillary GC ; capillary SFC ; diastereoisomeric esters ; optical resolution ; (S)-Trolox methyl ether ; primary alcohols ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (S)-Trolox methyl ether is known as a powerful chiral reagent for the e.e. determination of chiral alcohols by separation of the corresponding diastereoisomeric esters on achiral GC and SFC columns. In order to further improve his methodology, five possible candidates resultings from variation of structural elements of parent reagent have been tested for derivatization with selected alcohols and subsequent analysis of the diastereoisomeric pairs of esters. The results of this optimization procedure showing the ways to new potent reagents are discussed. © 1996 Wiley-Liss, Inc.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 19 (1998), S. 145-148 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A transient periodic stripe domain pattern is observed during photo-induced director reorientation of a sample containing rod-like block copolymer vesicles in a low molecular weight nematic liquid crystal.
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  • 3
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mechanism of the strictly alternating anionic copolymerization of phenyl glycidyl ether (PGE) and phthalic anhydride (PA) was initiated by various imidazoles. Because of the strictly alternating copolymerization polyesters with a repeating unit of PGE-PA were obtained. The mechanism of the reaction was analyzed by means of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). With this technique the molar masses of the oligomers, the molar mass of the repeating unit, the weight-average molar mass M̄w and the number-average molar mass M̄n, their ratio M̄w/M̄n and the residual molar mass could be calculated. The strictly alternating copolymerization was easy to prove because the molar masses of PGE and PA are slightly different. The question whether the initiator remains chemically bound during the whole reaction could be solved. To this end polyesters obtained by initiation with various imidazoles with different molar masses were synthesized. The calculated residual molar masses correspond exactly to the molar masses of the imidazoles.
    Additional Material: 3 Ill.
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  • 4
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Microgels were synthesized by intramolecular crosslinking of poly(vinyl alcohol) single chains with glutaraldehyde in dilute aqueous solutions (concentration c = 0,1 g/100 mL). The degree of crosslinking was varied from X = 0 to X = 150 (X is the number of crosslinker molecules per chain). The reaction products were characterized by static and dynamic light scattering and viscosity measurements. A clear shrinking of molecular dimensions could be observed with increasing degree of crosslinking, since the radius of gyration Rg, and with that, the p-parameter (p = Rg/Rh) decrease with the number of intramolecular crosslinks. A similar behavior is seen from viscosity measurements. The intrinsic viscosity [η] decreases with increasing X-parameter and depends only very weakly on the temperature which is an indication of a loss in flexibility and therefore for a relatively fixed structure.
    Additional Material: 7 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 223-237 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: AB and ABA block copolymers are synthesized by direct living anionic polymerization where the A-block is a liquid crystalline side chain polymer (LC-block) and the B-block is an isotropic polymer (I-block). Similar to amphiphilic block copolymers with a “hydrophilic” water soluble segment and a “hydrophobic” water insoluble part, the LC/I block copolymers consist of the “nematophilic” LC-block that is soluble in a nematic solvent and the “nematophobic” segment that is insoluble in nematic solvents. The behaviour of these LC/I block copolymers and corresponding homopolymers is analyzed in dilute nematic solutions of low molar mass liquid crystals. The effects of varying molecular weight, chemical constitution of blocks and block length ratio are investigated. Copolymers with a high fraction of the I-block are insoluble in the nematic solvent as indicated by phase separation. Copolymers with a high fraction of the LC-block are completely soluble. If the weight fraction of the LC-block is in the range of 0.46 to 0.85, thermoreversible thread-like aggregates are formed in the nematic solvent. These thread-like aggregates have a uniform diameter of 2-3 μm and their long axis perfectly follows the director field of the nematic matrix. The formation of these structures is discussed in terms of copolymer concentration, temperature and influence of aligning surfaces. From simple geometrical packing arguments it can be assumed that these thread-like aggregates consist of bilayered vesicles. In contrast to the spherical shape of amphiphilic block copolymer vesicles in aqueous solution, the rod-like shape of vesicles in nematic solution is caused by the minimization of free elastic energy density of the nematic matrix.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 1014-1015 
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 7
    ISSN: 0044-8249
    Keywords: Chalkogene ; Hypervalente Verbindungen ; Kationen ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 8
    ISSN: 0044-2313
    Keywords: bimetallic Fe—Ni complexes ; CO2 fixation ; nickelalactones ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Organometallic Chemistry of Binuclear 1-Azadiene-Nickel(0) Complexes: Bimetallic Compounds with a Ni—Fe Bond by Addition of Pentacarbonyl-iron(0) and Nickelalactons by Ring Opening Reaction of Cyclic AnhydridesThe binuclear nickel(0) complexes 1-3, which contain as well bridging 1-azadienes ligands as five or six-membered (N∩N)-chelate rings react at -30°C with Fe(CO)5 to form the bimetallic compounds 4-6, containing a Ni—Fe bond and two carbonyl groups as bridging ligands. The coordination of the [(bpy)Ni(0)] fragment to the olefin part of the 1-azadiene chain in 6 leads to the formation of the trinuclear complex 7, which can storage CO2 at the peripheral position. Succinic acid anhydride or glutaric acid anhydrid undergo a ring opening reaction by reacting with 3 yield nickelalactones upon elimination of CO.
    Notes: Die binuclearen Nickel(0)-Komplexe 1-3, die verbrückende 1-Azadieneinheiten und N∩N-Chelatfünf- oder Sechsringe enthalten, reagieren bei -30°C mit Fe(CO)5 zu den Bimetallcarbonylverbindungen 4-6, die eine Ni—Fe-Bindung und 2 CO-Brückencarbonylliganden aufweisen. Koordination des (bipy)Ni(0)-Fragments an den Olefinteil der 1-Azadienkette 6 liefert den Dreikernkomplex 7, der an der Peripherie CO2 speichert. Bernsteinsäureanhydrid oder Glutarsäureanhydrid reagieren mit 3 unter Ringöffnung und CO-Eliminierung zu Nickelalactonen.
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  • 9
    ISSN: 0044-2313
    Keywords: Zirconium ; Lithium ; Hydroxoligands ; Oxoligand ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: An Unusual Trimeric Bimetallic Li—Zr Complex with the Backbone [Zr3(μ2-OH)3(μ3-O)Li5] by Reaction of Zirconiumorgano and Hydrido Complexes with WaterThe reaction of compounds of the type [(LZr)(LiH)(L′)]n and [(LZr)(LiH)(L′)(alkyne)]n (L: 2,2′-Biphenolato-dianion, L′: thf, Bu3P, alkyne: Ph—C≡C—SiMe3, CH≡CH) with water at 0°C in a thf solution results in the formation of th trimeric bimetallic complex 8 [(L2Zr)3(μ2-OH)3(μ3-O)Li5(thf)8(H2O)5] in 50% yield. The X-ray analysis of 8 shows that a planar six-membered ring Zr3(μ2-OH)3 is formed. In the middle of this ring is a dianionic oxygen atom placed, coordinating to the three L2Zr centres in a planar μ3-coordination (bond angles 120,05μ). Five lithium ions stabilize the anionic backbone by bridging the biphenolato chelate ligands, which form seven-membered chelate rings with the atoms.1H-, 13C-, and 7Li-NMR spectra exhibit that the solid state structure remains unchanged in solution (thf).
    Notes: Die Reaktion von Verbindungen des Typs [(LZr)(LiH)(L′)]n und [(LZr)(LiH)(L′)(alkin)]n (L: 2,2′-Biphenolato-dianion, L′: thf, Bu3P, alkin: Ph—C≡C—SiMe3, CH≡CH) mit Wasser führt bei 0°C in thf in 50% Ausbeute zum trimeren Bimetallkomplex 8 [(L2Zr)3(μ2-OH)3(μ3-O) Li5(thf)8(H2O)5]. Die Kristallstrukturanalyse von 8 zeigt, daß ein planarer Zr3(μ2-OH)3-Sechsring gebildet wird. In seiner Mitte ist ein dianionisches Sauerstoffatom fixiert, das an den drei L2Zr-Zentren mit planarer μ3-Koordination gebunden ist (Bindungswinkel Zr—O—Zr 120,05°). Fünf Lithiumionen stabilisieren das anionische Gerüst durch Verbrückung der Biphenolatchelatliganden, die mit den Zr-Atomen Chelatsiebenringe ausbilden. 1H-, 13C- und 7Li-NMR-Spektren zeigen, daß in Lösung (thf) die Festkörperstruktur unverändert erhalten bleibt.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 1135-1143 
    ISSN: 0044-2313
    Keywords: Copper(I) ; 1-azadienes ; oxidation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Copper(I) Complexes with 1-Azadiene Chelate Ligands and Their Reaction with OxygenThe reaction of the bidendate 1-azadiene ligands Me2N—(CH2)n—N=CH—CH=CH—Ph with CuX results in the formation of the dimeric compounds [ACuX]2 and [BCuX]2 (A: n = 2, B: n = 3, X: I, Cl). The structure of complex 1 [ACuI]2 was determined by X-ray crystal structure analysis. 1 consists of two tetrahedrally coordinated Cu atoms connected by two iodo bridges. (Cu—Cu bond length: 261 pm).The ligand Me—N(CH2CH2N=CH—CH=CH—Ph)2 (C) reacts with CuX to form the monomeric complexes [CCuX] (5: X=I, 6: X=Cl). The crystal structure of 5 shows that the ligand acts as a tridendate ligand. The bond lengths of the CuN(sp2) bonds are significantly shorter than the Cu—N(sp3) distance.Reacting the podand-type ligands N(CH2CH2—N=CH—R)3 (D: R=Ph, E: R=-CH=CH—Ph) with CuX yields the ionic complexes 7 [DCu][CuCl2] and 8 [ECu][CuCl2]. 7 was characterized by X-ray analysis which confirmed that D acts as a four-dendate podand ligand.The compounds 1-8 are unreactive towards CO2 but take up O2 even at deep temperatures. At -78°C the orange-red complex 4 [BCuCl]2 reacts with O2 in CH2Cl2 to form a deep violet solution, but the primary product of the oxidation could not be isolated. It reacts at room temperature to form the green complex 9 [μ-Cl, μ-OH][BCuCl]2. The X-ray structure analysis of 9 confirms that a dimeric CuII complex is formed in which both a chloro- and a hydroxo group are bridging the monomeric units. The CuII centers exhibit a distorted tetragonal-pyramidal coordination.The pathway of the reaction with O2 will be discussed.
    Notes: Die Reaktion der zweizähligen 1-Azadienliganden Me2N—(CH2)n—N=CH—CH=CH—Ph mit CuX führt zu den dimeren Komplexen [ACuX]2 and [BCuX]2 (A: n = 2, B: n = 3, X: I, Cl). Die Struktur des Komplexes 1 [ACuI]2 wurde durch Kristallstrukturanalyse bestimmt. 1 enthält zwei tetraedrisch koordinierte Cu-Atome, die über zwei Iodobrücken miteinander verknüpft sind Cu—Cu-Bindungslänge: (261 pm).Der Ligand Me—N(CH2CH2N=CH—CH=CH—Ph)2 (C) reagiert mit CuX unter Bildung der monomeren Komplexe [CCuX] (5: X = I, 6: X=Cl). Die Kristallstruktur von 5 zeigt, daß der Ligand dreizählig koordiniert. Die Bindungslängen der Cu—N(sp2)-Bindungen sind signifikant kleiner als der Cu—N-(sp3)-Abstand.Die Reaktion der Podand-Liganden N(CH2CH2—N=CH—R)3 (D: R=Ph, E: R=-CH=CH—Ph) mit CuX führt zu den ionischen Komplexen 7 [DCu][CuCl2] bzw. 8 [ECu][CuCl2]. 7 wurde durch Röntgenstrukturanalyse charakterisiert, die ausweist, daß D als vierzähliger Ligand fungiert.Die Komplexe 1-8 sind gegenüber CO2 nicht reaktiv, nehmen aber O2 schon bei tiefen Temperaturen auf. Bei -78°C reagiert der orangerote Komplex 4 [BCuCl]2 mit O2 in CH2Cl2 zu einer tiefvioletten Lösung, das Primärprodukt der Oxidation konnte jedoch nicht isoliert werden. Es reagiert bei Raumtemperatur zu dem grünen Komplex 9 [μ-Cl, μ-OH][BCuCl]2. Die Kristallstrukturanalyse belegt, daß ein dimerer CuII-Komplex gebildet wird, in dem eine Chloro- und eine Hydroxobrücke die Monomereinheiten verbrücken. Die CuII-Zentren weisen eine verzerrt tetragonal-pyramidale Koordination auf.Der Reaktionsweg der Umsetzung mit O2 wird diskutiert.
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