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  • Chemistry  (87)
  • Polymer and Materials Science  (38)
  • bic Book Industry Communication::J Society & social sciences::JN Education  (6)
  • 2020-2024  (6)
  • 1990-1994  (83)
  • 1970-1974  (4)
  • 1
    Electronic Resource
    Electronic Resource
    New phenylboronic esters derived from inositol [1] (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 5 (1994), S. 139-143 
    Details
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have prepared two new tetracyclic phenylboronic esters 4 and 5 derived from myo-inositol and from 1,2-O-isopropylidene-myo-inositol, respectively. The structures of these compounds were established from NMR and IR spectra, elemental analyses, and an X-ray diffraction study in the case of 4. Compound 4 is a tetracyclic derivative of the less stable conformer of inositol (five axial hydroxy groups and one equatorial) with two dioxaboroline rings at opposite faces of the six-membered ring, one formed between the boron atom and the axial hydroxyl groups at C-3 and C-5 and the other between the boron atom and the hydroxyl groups at C-4 and C-6, and a dioxaborolidine ring bridging C-1 and C-2 at axial and equatorial positions. A similar structure was found for 5 with the difference that bridging C-1 and C-2 there is a dioxolane ring. The boron atoms are planar with their attached atoms, stabilized by retrocoordination between the boron and oxygen and carbon atoms, respectively. The two phenyl rings that are in the same face of the molecule are essentially parallel, with a dihedral angle between planes of 28.26 ± 0.79°.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hc.520050210
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  • 2
    Electronic Resource
    Electronic Resource
    Fragmentation of vinyl triflates by electron impact. Mechanism of an unusual double hydrogen atom transfer reaction (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 427-431 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The main fragmentation pathway of vinyl triflates in mass spectra involves the loss of CF3SO2·, followed by the loss of olefin and/or CO. The loss of TfOH takes place with fragmentation of a vinylic C—H bond. TfOH2+ ions are formed via regiospecific double hydrogen transfer from five- and six-membered cyclic triflates.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290080517
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  • 3
    Electronic Resource
    Electronic Resource
    Electron impact mass spectrometry of triterpenoids from guayuleContribution No. 998 from the Instituto de Química, UNAM, Mexico. (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 25 (1990), S. 237-238 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210250411
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  • 4
    Electronic Resource
    Electronic Resource
    The number of Kα photons produced on a set of thin targets as a functional description of the fluorescence exciting x-ray beamPresented at the European Conference on EDXRS, Myconos, Greece, 30 May-6 June 1992. (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 22 (1993), S. 312-316 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: This work suggests a theoretical approach for the description of a primary x-ray beam by means of the K fluorescence which it excites on a set of thin targets made of pure elements. Physical quantities, defined as weighted integrals over hv of the photon spectral distribution, are obtained directly as weighted integrals of the Kα yields over the variable Ez (the ionization energy of the K shell of the element with atomic number Z), without needing any explicit reconstruction of the spectral distribution. The set of Kα yields produced by an x-ray beam as a function of Ez is a functional description of the exciting beam. Theoretically, such a description is suited to x-ray fluorescence analysis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300220425
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  • 5
    Electronic Resource
    Electronic Resource
    1H, 13C, 15N, 113Cd, 2D 15N—1H and solid-state 13C CP/MAS NMR of Hg and Cd complexes of 4(1H)-quinazolinone-2,3-dihydro-2-thioxo (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 832-835 
    Details
    ISSN: 0749-1581
    Keywords: 1H, 13C, 15N and 113Cd NMR ; Two-dimensional NMR ; CP/MAS NMR ; Hg and Cd complexes 4(1H) -Quinazolinone-2,3-dihydro-2-thioxo ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Cd(II) and Hg(II) complexes of 4(1H)-quinazolinone-2,3-dihydro-2-thioxo (1) and the free ligand were studied by 1D and 2D multinuclear magnetic resonance in solution and 13C cross polarization magic angle spinning NMR in the solid state. Compound 1 adopts only one of five possible tautomeric structures in solution, namely the thiouracyl-like structure. It was found that the metal atom is linked to two molecules of deprotonated 1 by N-1 and coordinated by the sulphur atom. The compounds retain the same structure in the solid state and in dimethyl sulphoxide solution.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260310908
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  • 6
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    Identificación y Recuperación de Valores Ancestrales Afrocolombianos en la Región Pacífico (2022)
    Universidad Santiago de Cali | Lenguajeando mediación pedagógica
    Details
    Publication Date: 2024-03-29
    Description: Based on the roots and convictions of the researchers - the rhizomatic study ventured into the identification and recovery of Afro-Colombian ancestral values in the Pacific Region (Colombia), generating two sequential and complementary stages for this purpose: language contact with elders and older adults from two Ancestral Black Communities Councils in Buenaventura and in La Playa respectively (Valle-Colombia), and the subsequent pedagogical mediation with young people from the Ancestral Black Communities Council of La Bocana (Valle-Colombia). From a rhizomatic methodological structure based on the positions of Deleuze andGuattari (2005), the respective interactions were conducted in a holistically way, under the recovery of human networks and language, in addition to dynamics such as the cane handover, all of the former with strong roots in the praxis of Afro-Colombian communities in general. The obtained results led to significant findings both at the axiological level, and in the terms of emerging cultural elements, in its final phase the research allowed to assertively show the realization of padagogical mediations achieving to reaffirm and recover the Afro-Colombian ancestral values in the context of their new generations.
    Description: Published
    Description: Dadas las raíces y convicciones de los investigadores, el estudio rizomático incursionó en la identificación y recuperación de los valores ancestrales afrocolombianos en la Región Pacifico (Colombia), generándose para el efecto dos etapas secuenciales y complementarias: el contacto de lenguajeo con ancianos y adul-tos mayores de dos Consejos Comunitarios Ancestrales de Comunidades Negras, respectivamente de Buenaventura y de La Playa (Valle–Colombia), y la posterior mediación pedagógica con jóvenes del Consejo Comunitario Ancestral de Comunidades Negras de La Bocana (Valle–Colombia). Desde una estructura metodológica rizomática asentada en las posturas de Deleuze y Guattari (2005), las respectivas interactuaciones de adelantaron de manera holística, bajo la recuperación de tejidos humanos y lenguajeos, además de dinámicas como el paso del bastón, todas con fuerte arraigo en las praxis de las comunidades afrocolombianas en general. Los resultados obtenidos conllevaron a significativos hallazgos tanto a nivel axiológico, como en cuanto a elementos culturales emergentes, y siendo que en su fase final la investigación permitió mostrar de manera asertiva la realización de mediaciones pedagógicas que logran reafirmar y recuperar los valores ancestrales afrocolombianos en el contexto de sus nuevas generaciones.
    Keywords: Afrocolombianos ; Identificación ; Recuperación ; Región Pacífico ; Valores Ancestrales ; bic Book Industry Communication::J Society & social sciences::JN Education ; thema EDItEUR::J Society and Social Sciences::JN Education
    Language: Spanish
    Format: application/pdf
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    E-BOOK
  • 7
    Electronic Resource
    Electronic Resource
    New oligomers with isatin. Condensation reactions of thiophene and 2,2′-bithiophene with isatin (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 1-16 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die seit langem in der Literatur als “Indophenin-Reaktion” bekannte Umsetzung von Isatin mit Thiophen wurde systematisch untersucht und auf die Umsetzung mit Bithiophen erweitert. Die Reaktionsprodukte wurden isoliert und durch FT-IR, UV, 1H-NMR, 13C-NMR sowie GPC charakterisiert.Im Gegensatz zu den Literaturdaten wurden Reaktionsprodukte mit höheren Molgewichten und anderer Molmassenverteilung gefunden. Die Reaktionsbedingungen - Lösungsmittel, Temperatur und Konzentration - sind für den Reaktionsablauf und die entstehenden Produkte von entscheidender Bedeutung.Füur die oligomeren Reaktionsprodukte werden neue Strukturen vorgeschlagen, die in Übereinstimmung mit allen analytischen Daten sind. Anhand eines Formelschemas werden die Reaktionen des Isatins mit Thiophen (Bithiophen) erläutert.
    Notes: A systematic study of the well-known indophenin reaction between isatin and thiophene was extended to embrace bithiophene. The products of the reactions were isolated and characterized by FT-IR, UV, 1H-NMR, 13C-NMR, and GPC. The values of the thus determined molar masses and molar mass distributions differed from the data given in the literature. The reaction conditions - solvent, temperature, and concentration - are of crucial importance for the course of the reaction and the products obtained.New structures suggested for the oligomeric reaction products agree with all the analytical data. The reactions between isatin and thiophene (bithiophene) are explained schematically.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051780101
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  • 8
    Electronic Resource
    Electronic Resource
    Computer simulation of hydrodynamic properties of semiflexible macromolecules: Randomly broken chains, wormlike chains, and analysis of properties of DNA (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 883-900 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The translational and rotational diffusion coefficients and the intrinsic viscosity of semiflexible, randomly broken, and wormilike chains have been obtained by Monte Carlo simulation in the context of the rigid-body treatment. Both approximate and rigorous rigid-body hydrodynamics are used, so that the error introduced by the approximate methods can be evaluated. A randomly broken chain and a wormilike chain having the same contour length and persistence length have the same radius of gyration but different values for any of the hydrodynamic properties. The two types of chains are compared in this regard. Considering that the cross section of the chain is represented by a cylinder better than by a string of spheres, we devise a cylindrical correction to be applied to the results simulated for chains of beads. Application is made to the analysis of experimental data for the translational and rotational coefficients of DNA fragments with up to 103 base pairs, obtaining the persistence length for each model. The values for the wormlike chain agree well with model-independent values obtained from radii of gyration and with other literature data at varying ionic strength. The randomly broken chain is equally able to reproduce the experimental length dependence of the properties, but the resulting persistence length may be too high.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290603
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  • 9
    Electronic Resource
    Electronic Resource
    Reactivity of Dithiazinanes towards BH3, BD3 and BF3. New Heterocycles: 5,5-Dimethyl-1,3-dithia-5-azonia-4-boratacyclohexane and 6,6-Dideuterio-5-methyl-5[D1]methyl-1,3-dithia-5azonia-4-boratacyclohexane. A Method for the Dimethylation and Monodeuteriomethylation of Primary Amines (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 863-867 
    Details
    ISSN: 0009-2940
    Keywords: Dithiazinanes ; Dithiazoniaboratacyclohexane ; Amines: dimethylation and monodeuteriomethylation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 5-Methyl-and 5-tert1-butyl-1,3,5-dithiazinane (1 and 7) react with BH3·THF, and Et2O·BF3 to yield the N1-coordinated adducts 2 - 4 (with BH3, BD3, and BF3, respectively). The conformations and spectroscopic properties of the adducts are discussed. The reactions of 1 and 7 with BY3·THF lead to the six-membered boron heterocycles 5,5-dimethyl-1,3-dithia-5-azonia-4-boratacyclohexane (5), 4,4-dideuterio-5-methyl-5[D1]methyl-1,3-dithia-5-azonia-4-boratacyclohexane (6), and 5-tert1-butyl-5-methyl-1,3-dithia-5-azonia-4-boratacy-clohexane (8). Compounds 2 and 5 are isolobal isomers. The reaction of BH3 or BD3 with 7 affords, after heating, tert1-butyldimethylamine - borane (9) and tert1-butyldi([D1]methyl)1-amine - trideuterioborane (11), respectively. The dithiazinane derivatives may be used in organic synthesis for the dimethylation of primary amines and the preparation of alkyldimethylamines with monodeuterated methyl groups.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260403
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  • 10
    Electronic Resource
    Electronic Resource
    From Azole - Borane Adducts to Azaboles  -  Molecular Structure of an Imidazabole (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 343-346 
    Details
    ISSN: 0009-2940
    Keywords: Azole-borane adducts ; Azaboles ; Imidazabole ; X-ray analysis ; NMR, multinuclear ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Elimination of H2 from the imidazole - borane adduct 1 leads to a mixture of the imidazaboles 2 and 2′. The symmetrical isomer 2 (two H2BNC fragments) is isolated in pure state and characterized by an X-ray structure analysis (monoclinic, space group P21). 2-(Trimethylstannyl)thiazole (3a) and 1-methyl-5-(trimethylstannyl)-1,2,4-triazole (3b) react with triethylborane to form adducts 4 from which, in the presence of an excess of Et3B, tetraalkyltin is elimated to give the thiazabole 5a and the triazabole 5b, respectively. Multinuclear 1H-, 11B-, 13C-, 14N-, and 119Sn-NMR spectroscopy serve for following the reactions (compounds 3 to 5) and to characterize all final products.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270210
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