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  • Artikel: DFG Deutsche Nationallizenzen  (19)
  • Organic Chemistry  (19)
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  • Artikel: DFG Deutsche Nationallizenzen  (19)
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  • 1
    Digitale Medien
    Digitale Medien
    Polarographische Untersuchungen an symmetrischen Triazacarbocyaninen in Methanol (1983)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 66 (1983), S. 661-668 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Polarographic Investigations on Symmetrical Triazacarbocyanine Dyes in MethanolThe reduction mechanism of eleven symmetrical triazacarbocyanine dyes with different heterocycles in methanol (containing lithium chloride or lithium acetate/acetic acid) has been investigated by means of polarography, cyclic oscillopolarography and coulometry.The reduction occurs in a reversible to irreversible two electron transfer step, followed by an irreversible chemical step. Reduction potentials, transfer coefficients and specific currents have been measured and compared with properties measured in acetonitrile.The effect of substituents X has been studied on the compounds 1-ethyl-2-[3-(1-ethyl-6-X-1,2-dihydroquinolin-2-ylidene)-1-triazeno]-6-X-quinolinium tetrafluoroborate 1f(X) and 3-ethyl-2-[3-(3-ethyl-5-X-Δ4-1, 3-thiazolin-2-ylidene)-1-triazeno]-5-X-1, 3-thiazolium tetrafluoroborate 1g(X), and ρ-values of 0.20 and 0.40 V, respectively, have been found.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19830660228
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  • 2
    Digitale Medien
    Digitale Medien
    Photoisomerisierung und Relaxation symmetrischer Triazacarbocyanine in einem Alkoholgemisch (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1394-1400 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Photoisomerization and Relaxation of Symmetrical Triazacarbocyanine Dyes in an Alcoholic Mixture at Low TemperatureThe partial photobleaching of a series of symmetrical triazacarbocyanine dyes with different heterocycles in EtOH/MeOH/i-PrOH at low temperature (110 to 250 K) was investigated by UV/VIS spectra. Kinetic data of the dark reaction of photobleached compounds are given. The effect of electron-donating or -accepting substituents, respectively, and of protonation of the photobleached compound on kinetic data and on UV/VIS spectra was studied. Products of photobleaching and mechanisms of the dark reaction are discussed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19850680531
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  • 3
    Digitale Medien
    Digitale Medien
    Lösungsmittel-, Viskositäts-, Säure- und Substituenteneinflüsse auf die Photoisomerisierung und Relaxation symmetrischer Triazacarbocyanine bei 283 bis 323 K (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1401-1405 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Influence of Solvents, Viscosity, Acid, and Substituents on the Photoisomerization and the Relaxation of Symmetrical Triazacarbocyanine Dyes at 283 to 323 KPhotobleaching and the reverse dark reaction of seven symmetrical triazacarbocyanine dyes with different heterocycles were studied dependent on solvent effects (protic and aprotic solvents), on effects of viscosity (glycerol/EtOH mixtures), and on effects of added acid. No effects of dissolved O2 or added I2 has been observed. Kinetic data (ΔH≠, ΔS≠, and ΔG298 K≠) of the reverse reaction are given. The effect of the substituents has been studied on two series of substituted triazacarbocyanine dyes. The mechanism of the reverse reaction is discussed.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19850680532
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  • 4
    Digitale Medien
    Digitale Medien
    Flash Photolysis of 5-Methyl-1,4-naphthoquinone in Aqueous Solution: Kinetics and mechanism of photoenolization and of enol trappingDedicated to our colleague Fabian Gerson who is venturing to new shores (1997)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 80 (1997), S. 1106-1121 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 5-Methyl-1,4-naphthoquinone (1) is a remarkable probe to study hydrogen and proton transfer reactions. The photoenol 4-hydroxy-5-methylidene naphthalen-1 (5H)-one (2) is formed in the ground state within 2 ps of excitation and with a quantum yield of unity, presumably through a conical intersection of the S0 and S1 hypersurfaces. In aqueous acid, enol 2 is hydrated to 5-(hydroxymethyl)naphthalene-1,4-diol 3 (X = OH, Scheme 1). The rate of hydration of 2 increases linearly with acid concentration from ca. 1.5 × 104 s-1 at pH 6 to reach a maximum value of 9 ×107 s-1 when the remaining carbonyl function is protonated, pKa(2+) = 1.1. Contrary to an earlier suggestion, the rate-determining step in the acid-catalyzed hydration of 2 is addition of water to the conjugate acid 2+. Pronounced acceleration of the decay rate of 2 by hydrazoic-acid buffers indicates competitive trapping of 2+ by the azide ion. In neutral-to-weakly-basic solutions, enol 2 reacts by ionization, pKa(2) = 6.5, and nearly diffusion-controlled condensation of the carbanionic species 2- with quinone 1. Proto-nation at the methylidene C-atom does not compete measurably with protonation on carbonyl O-atom, despite a Substsial thermodynamic basic for carbon Portoation of ca. 50 kJ mol-1 for 2 and 100 mol-1 for 2-.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19970800408
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  • 5
    Digitale Medien
    Digitale Medien
    Polarographische Untersuchungen an symmetrischen Triazacarbocyaninen in Acetonitril (1981)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 1522-1532 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Polarographic Investigations on Symmetrical Triazacarbocyanine Dyes in Acetonitrile SolutionThe reduction behaviour of thirteen symmetrical triazacarbocyanine dyes with different heterocycles in acetonitrile solution has been investigated by means of dc- and ac-polarography, cyclic oscillopolarography and coulometry.The reduction mechanism has been found to be of the type eec with the first step being reversible and the second step being reversible to irreversible. Reduction potentials, transfer coefficients and specific currents of both steps have been measured (E1/2: -0,110 to -1.025 V vs. Ag/AgCl for the first step) and compared with known properties of carbocyanines and triazenium salts and to HMO calculations.The effect of substituents X has been studied on the compounds 1,3-diethyl-2-[(1,3-diethyl-5-X-benzimidazolin-2-yliden)triazenyl]-5-X-benzimidazolium-tetra-fluoroborate (1a (X)) and 3-ethyl-2-[(3-ethyl-5-X-Δ4-1,3-triazolin-2-yliden)triazenyl]-5-X-1,3-thiazolium-tetrafluoroborate (1g(X)), and p-values of 0,36 and 0,72 V, respectively, have been found.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19810640528
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  • 6
    Digitale Medien
    Digitale Medien
    Azidinium-Salze. 25. Mitteilung24. Mitteilung: [1].. Symmetrische Azopyridinon-Farbsalze: Synthese, spektrophotometrische und acidobasische Eigenschaften, Metallkomplex-Bildung und kinetische Untersuchung der Azo-Kupplung (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 216-230 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Symmetrical Azopyridinone Dyes: Synthesis, Spectrophotometrical and Acidobasic Properties, Metal-Complex Formation and Kinetical Investigation of the Azo-Dye FormationThe 13 substituted symmetrical azopyridinone dyes 2a-n were synthesized and their VIS spectra measured. The pK*a values of some dyes and of pyridinone coupling components were determined in MeOH/H2O 64:36. The metal-complex formation of the dyes with Cd2+, Zn2+, Co2+, Ni2+, and Cu2+ was investigated, and complex-formation constants of the 1:1 complexes were determined in H2O for 2k (Table 2) and in dimethylformamide/H2O 1:1 for some other azopyridinone dyes (Table 3). The mechanism of the azo-dye formation was investigated and found to be much more complicated than expected. A mechanism of the coupling reaction was developed (see Scheme 4) and fitted by least-squares calculations.
    Notizen: NO ABSTRACT.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19940770124
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  • 7
    Digitale Medien
    Digitale Medien
    Voltammetrische Untersuchungen der Oxydation der symmetrischen Triazacarbocyanine in Acetonitril (1984)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 765-769 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Voltammetric Investigations on the Oxidation Step of Symmetrical Triazacarbocyanine Dyes in Acetonitrile SolutionThe oxidation behaviour of twelve symmetrical triazacarbocyanine dyes with different heterocycles in MeCN (containing tetrabutylammonium perchlorate) has been investigated by means of dc-, ac- and cyclic triangular wave voltammetry. The oxidation mechanism has been found to be of the type ec, with the electrochemical step being reversible to irreversible. Oxidation potentials and transfer coefficients have been measured (E1/2 1.60 to 2.12 V vs. Ag/AgCl) and compared with known properties of carbocyanines. The effect of substituents X has been studied on the compounds 1,3-diethyl-2-[3-(1,3-diethyl-5-X-benzimidazolin-2-ylidene)-1-triazeno]-5-X-benzimidazolium tetrafluoroborate ((1a(X)) and 3-ethyl-2-[3-ethyl-5-X-Δ4-1,3-thiazolin-2-ylidene)-1-triazeno]-5-X-1,3-thiazolium tetrafluoroborate (1g(X)), and ρ-values of 0.425 and 0.565 V, respectively, have been found.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19840670317
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  • 8
    Digitale Medien
    Digitale Medien
    Polarographische und voltammetrische Untersuchungen an symmetrischen Methin-, Azamethin- und Phosphamethincyaninen in Acetonitril (1984)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 770-773 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Polarographic Investigations on Symmetrical Methine-, Azamethine-, and Phosphamethinecyanine dyes in Acetonitrile SolutionThe reduction and oxidation behaviour of six symmetrical methine-, azamethine-, and phosphamethine dyes with different heterocycles in MeCN solutions has been investigated by menas of dc- and ac-polarography (DME, MDE and rotating Pt-electrode) and cyclic triangular wave voltammetry. The reduction and oxidation mechanism has been found to be of the type ec with the reduction and oxidation step being reversible to irreversible. Reduction and oxidation potentials, transfer coefficients, and specific currents have been measured and compared with known properties of methinecyanines, carbocyanines, and triazacarhocyanines.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19840670318
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  • 9
    Digitale Medien
    Digitale Medien
    Halochrome Molekeln 3. Mitteilung [1]. Thermodynamische und kinetische Untersuchungen zum acidobasischen Verhalten substituierter 6,6-Diphenyl-6H-chromeno[4,3-b]indole (1980)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 1284-1293 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Halochromic Molecules. Thermodynamics and Kinetics of the Acidobasic Behaviour of Substituted 6,6-Diphenyl-6H-Chromeno [4,3-b]IndolesThe complex halochromic behaviour of substituted 6, 6-Diphenyl-6 H-chromeno-[4,3-b]indoles was investigated by stopped flow techniques and spectrometric methods in 64% methanol/water mixtures at 25°. pK-values are determined, rates and mechanisms of coloration reaction are investigated and results are discussed.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19800630519
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  • 10
    Digitale Medien
    Digitale Medien
    Tetrazinodi(heteroarene): Voltammetrische und cyclovoltammetrische Untersuchung der Oxidation in Methanol, Acetonitril und Dichlormethan (1986)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 1531-1534 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Tetrazinodi(heteroarenes): Voltammetric and Cyclovoltammetric Studies of the Oxidation in Methanol, Acetonitrile, and DichloromethaneThe oxidation of seven symmetrical [1,2,4,5]tetrazinodi(heteroarenes) with different heterocycles has been investigated by means of dc, ac, and cyclic triangular voltammetry in MeCN and CH2Cl2 (containing Bu4NClO4), MeOH (containing LiCl) and in MeOH/H2O (equimolar mixture). The two step oxidation mechanism has been found of type ‘e-e’ with quasi-reversible electrochemical steps. Oxidation potentials and transfer coefficients have been measured (0 to +0.5 V vs. Ag/AgCl/3.5M KCl for the first oxidation step and potential differences of 0.8 to 1.3 V to the second oxidation step), indicating a high radical-ion stability.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19860690625
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