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  • General Chemistry  (6.879)
  • Atomic, Molecular and Optical Physics  (745)
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  • kinetics
  • Wiley-Blackwell  (7.624)
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  • 2000-2004  (455)
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  • 1
    Digitale Medien
    Digitale Medien
    The effects of aqueous solvent structure on the mutarotation kinetics of glucose (1977)
    Springer
    Journal of solution chemistry 6 (1977), S. 203-216 
    Details
    ISSN: 1572-8927
    Schlagwort(e): Glucose ; kinetics ; mixed solvent ; kinetic isotope effect ; enthalpy of activation ; entropy of activation ; tetrahydrofuran ; tert-butanol ; mutarotation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The mutarotation rates of glucose in aqueous mixtures of tetrahydrofuran andtert-butanol in the mole fraction (xi) range 0〈xi〈0.2 have been measured at 5° intervals in the range 5–35°C. The kinetic deuterium isotope effects have been determined for the same solvent compositions at 25 and 35°C. A statistical analysis of the Arrhenius plots indicates that the experimental errors, although small, are too large for the establishment of any compensation behavior between ΔH
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00646739
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  • 2
    Digitale Medien
    Digitale Medien
    Solvent effects on the acid-catalyzed hydrolysis of tetramethylurea (1976)
    Springer
    Journal of solution chemistry 5 (1976), S. 163-169 
    Details
    ISSN: 1572-8927
    Schlagwort(e): Solvent effects ; tetramethylurea ; hydrolysis ; hydrogen bonding ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Tetramethylurea was hydrolyzed in aqueous hydrochloric acid at temperatures of 80, 90, and 100°C. All reactions were carried out in an excess of both tetramethylurea and water, with first-order dependence on acid concentration being observed. As the concentration of water was increased, the rate of hydrolysis decreased until equimolar amounts of water and tetramethylurea were present. Subsequent addition of water had no effect on the observed rate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00654333
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  • 3
    Digitale Medien
    Digitale Medien
    Why Does the Linear Driving Force Model for Adsorption Kinetics Work? (2000)
    Springer
    Adsorption 6 (2000), S. 137-147 
    Details
    ISSN: 1572-8757
    Schlagwort(e): adsorption ; kinetics ; linear driving force model ; process design
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The Linear Driving Force (LDF) model for gas adsorption kinetics is frequently and successfully used for analysis of adsorption column dynamic data and for adsorptive process designs because it is simple, analytic, and physically consistent. Yet, there is a substantial difference in the characteristics of isothermal batch uptake curves on adsorbent particles by the LDF and the more rigorous Fickian Diffusion (FD) model. It is demonstrated by using simple model systems that the characteristics of the adsorption kinetics at the single pore or the adsorbent particle level are lost in (a) evaluating overall uptake on a heterogeneous porous solid, (b) calculating breakthrough curves from a packed adsorbent column, and (c) establishing the efficiency of separation by an adsorptive process due to repeated averaging of the base kinetic property. That is why the LDF model works in practice.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008965317983
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  • 4
    Digitale Medien
    Digitale Medien
    Effect of K, Cs and Ba on the kinetics of NH3 synthesis over carbon-based ruthenium catalysts (2000)
    Springer
    Catalysis letters 68 (2000), S. 163-168 
    Details
    ISSN: 1572-879X
    Schlagwort(e): ammonia synthesis ; kinetics ; ruthenium catalysts ; promotional effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of NH3 synthesis over carbon-based ruthenium catalysts promoted with barium or alkali was studied. Both the ammonia partial pressure dependencies of the reaction rates (T = 400°C, p = 63 bar, H2 : N2 = 3 : 1) and the pressure variations of the activity (T = 370°C, p= 4–63 bar, H2 : NN2 = 3 : 1) were found to be different for Ba and for the alkali (K, Cs). Ba–Ru/C proved to be more sensitive to the NH3 content and to the total pressure. The rate of synthesis over the alkali-promoted catalysts is, in turn, much stronger influenced by the ruthenium dispersion. TOFs of NH3 synthesis for the promoted samples at 370°C and 4 bar (Ba 0.085 1/s, Cs 0.05 1/s, K 0.035 1/s) are significantly higher than that for the Ru(0001) basal plane (0.0085 1/s results from the literature data at 370°C, 2 bar). The most active Ru/C samples (Ba or Cs) exceed significantly the fused iron catalyst, especially at high conversions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019024629261
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  • 5
    Digitale Medien
    Digitale Medien
    Mechanism of the hydrodenitrogenation of o-toluidine and methylcyclohexylamine over NiMo/γ-Al2O3 (2000)
    Springer
    Topics in catalysis 11-12 (2000), S. 327-333 
    Details
    ISSN: 1572-9028
    Schlagwort(e): hydrodenitrogenation ; toluidine ; methylcyclohexylamine ; kinetics ; nickel-promoted molybdenum sulphide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The hydrodenitrogenation (HDN) of o-toluidine and its reaction intermediates was studied over a NiMo/γ-Al2O3 catalyst. The kinetics of the HDN of methylcyclohexylamine and of the hydrogenation of cyclohexene were also studied. Hydrogenation of o-toluidine alone produces methylcyclohexene and methylcyclohexane. When a sufficient quantity of cyclohexene is added during the HDN of toluidine, methylcyclohexylamine, the first intermediate in the hydrogenation of toluidine, becomes detectable. Because of its strong adsorption constant and high rate constant for reacting further to methylcyclohexene and methylcyclohexane, methylcyclohexylamine is not observed in the HDN of toluidine. Adding cyclohexene decreases the adsorption of methylcyclohexylamine, thus enabling its detection. The rate and adsorption constants of methylcyclohexylamine and cyclohexene in the HDN of methylcyclohexylamine were calculated by fitting the kinetic data to a Langmuir–Hinshelwood equation. A two-site model was used to describe the surface reactions, with one site for the methylcyclohexylamine reactions and the other for the cyclohexene reaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1027208200169
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  • 6
    Digitale Medien
    Digitale Medien
    Static and Kinetic Studies on the Adsorption Behavior of Sulfadiazene (2000)
    Springer
    Adsorption 6 (2000), S. 349-357 
    Details
    ISSN: 1572-8757
    Schlagwort(e): sulfadiazene ; adsorption ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract To investigate the nature of interactive forces between sulfadiazene molecules and alumina surface the experiments were performed for the adsorption of sulfadiazene (SD) from its aqueous sulution onto the alumina surfaces at 25 ± 0.2°C and the influence of factors such as increasing concentration of SD (4.0–20.0 × 10−3 mol cm−3), the time required for adsorption equilibrium, pH (2.0–12.0) and temperature (5–45°C) of the adsorption medium, the presence of ions like Cl−, SO2− 4 and PO3− 4 (0.01–0.30 M) and organic solvents (5% v/v) were observed on the course of adsorption of SD. Various adsorption and kinetic parameters such as adsorption coefficient, the rate constants for adsorption and desorption were also evaluated. The results of the above cited studies facilitated to formulate the mechanisms of interaction between SD and alumina surfaces. From application view point the present work may be a potential tool for an effective chromatographic separation of sulfa drugs from industrial effluents.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026517117239
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  • 7
    Digitale Medien
    Digitale Medien
    NO reduction over La2O3 using methanol (2000)
    Springer
    Catalysis letters 64 (2000), S. 65-75 
    Details
    ISSN: 1572-879X
    Schlagwort(e): NO reduction ; CH3OH ; La2O3 ; methyl nitrite ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Nitric oxide (NO) reduction by methanol was studied over La2O3 in the presence and absence of oxygen. In the absence of O2, CH3OH reduced NO to both N2O and N2, with selectivity to dinitrogen formation decreasing from around 85% at 623 K to 50–70% at 723 K. With 1% O2 in the feed, rates were 4–8 times higher, but the selectivity to N2 dropped from 50% at 623 K to 10% at 723 K. The specific activities with La2O3 for this reaction were higher than those for other reductants; for example, at 773 K with hydrogen a specific activity of 35 μmol NO/s m2 was obtained whereas that for methanol was 600 μmol NO/s m2. The Arrhenius plots were linear under differential reaction conditions, and the apparent activation energy was consistently near 14 kcal/mol with CH3OH. Linear partial pressure dependencies based on a power rate law were obtained and showed a near‐zero order in CH3OH and a near‐first order in H2. In the absence of O2, a Langmuir–Hinshelwood type model assuming a surface reaction between adsorbed CH3OH and adsorbed NO as the slow step satisfactorily fitted the data, and the model invoking two types of sites provided the best fit and gave thermodynamically consistent rate constants. In the presence of O2 a homogeneous gas‐phase reaction between O2, NO, and CH3OH occurred to yield methyl nitrite. This reaction converted more than 30% of the methanol at 300 K and continued to occur up to temperatures where methanol was fully oxidized. Quantitative kinetic studies of the heterogeneous reaction with O2 present were significantly complicated by this homogeneous reaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019036431195
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  • 8
    Digitale Medien
    Digitale Medien
    Oxidation of dicyclopentadiene catalyzed by palladium(II) acetate and p-benzoquinone in the presence of inorganic acid (2000)
    Springer
    Catalysis letters 69 (2000), S. 103-107 
    Details
    ISSN: 1572-879X
    Schlagwort(e): dicyclopentadiene ; Wacker oxidation ; Pd(AcO)2 ; benzoquinone ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The oxidation of dicyclopentadiene catalyzed by palladium(II) acetate and benzoquinone in the presence of perchloric acid was studied. Tricyclodecenone in high selectivity (85–98%) at a conversion of dicyclopentadiene up to 76% was obtained. The kinetic model assumed the significant inhibition complexation between dicyclopentadiene and tricyclodecenone with the catalytic species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019053402854
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  • 9
    Digitale Medien
    Digitale Medien
    Influence of acetylsalicylic acid on the renal handling of a spironolactone metabolite in healthy subjects (1976)
    Springer
    European journal of clinical pharmacology 10 (1976), S. 43-48 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Spironolactone ; acetylsalicylic acid ; fludrocortisone ; kinetics ; pharmacology ; interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The influence of 600 mg acetylsalicylic acid (ASA) on the renal excretion and clearance of canrenone, the principal unconjugated metabolite of spironolactone, was examined in a double-blind crossover study in six healthy subjects. ASA significantly reduced the urinary excretion, and the fractional excretion, of canrenone between 4 — 6 hours after administration of 50 mg spironolactone. The pharmacological activity of spironolactone, assessed simultaneously by alterations in fludrocortisone-induced urinary electrolyte changes, was slightly but not significantly reduced. The reductions in urinary canrenone excretion correlated with changes in the urinary log 10 Na/K ratio. The results suggest that canrenone may be actively secreted at the proximal renal tubule, and that secretion is blocked by ASA or its conjugates. This is a possible mechanism for the pharmacological interaction between ASA and spironolactone which has been described previously.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00561548
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  • 10
    Digitale Medien
    Digitale Medien
    Kinetics and efficacy of theophylline in the treatment of apnea in the premature newborn (1978)
    Springer
    European journal of clinical pharmacology 13 (1978), S. 203-207 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Theophylline ; kinetics ; apnea ; premature newborns ; developmental pharmacology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Aminophylline (theophylline-ethylenediamine) was administered to 27 premature newborns to prevent apneic spells. Of the 22 patients monitored for theophylline concentration, a therapeutic blood level was reached in 19 in 1–2 days, and 3 stayed below it. ‘Toxic’ blood levels (≥20 µg/ml) were reached in 3 cases, one of whom showed signs of toxicity. Theophylline treatment was not efficient in the prevention of apnea when a serious underlying disease was present. Theophylline blood half-life (mean : 27.0 h) and clearance (mean 12.9 ml/h/kg) confirmed the slow elimination pattern of the drug in the premature infant.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00609983
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