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  • kinetics
  • Springer  (37)
  • 1995-1999
  • 1990-1994  (37)
  • 1940-1944
  • 1994  (37)
Collection
Keywords
Publisher
Years
  • 1995-1999
  • 1990-1994  (37)
  • 1940-1944
Year
  • 1
    Electronic Resource
    Electronic Resource
    The kinetics of the solvolysis of chloropentacyanocobaltate(III) ions in water containing 2-methoxyethanol or diethylene glycol: A contrast with the effect of more hydrophobic cosolvents (1994)
    Springer
    Journal of solution chemistry 23 (1994), S. 1089-1100 
    Details
    ISSN: 1572-8927
    Keywords: Solvolysis ; kinetics ; aqueous solvent mixtures ; Co(III) complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of the solvolysis of [Co(CN)5Cl]3− have been investigated in water +2-methoxyethanol and water + diethylene glycol mixtures. Although the addition of these linear hydrophilic cosolvent molecules to water produces curvature in the variation of log(rate constant) with the reciprocal of the dielectric constant, their effect on the enthalpy and entropy of activation is minimal, unlike the effect of hydrophobic cosolvents. The application of a Gibbs energy cycle to the solvolysis in water and in the mixtures using either solvent-sorting or TATB values for the Gibbs energy of transfer of the chloride ion between water and the mixture shows that the relative stability of the emergent solvated Co(III) ion in the transition state compared to that of Co(CN)5Cl3− in the initial state increases with increasing content of cosolvent in the mixture. By comparing the effects of other cosolvents on the solvolysis, this differential increase in the relative stabilities of the two species increases with the degree of hydrophobicity of the cosolvent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00976258
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  • 2
    Electronic Resource
    Electronic Resource
    Thermodynamics of coupled reactions by the method of dynamic titration: the Nickel(II)-salicylate ion system (1994)
    Springer
    Journal of solution chemistry 23 (1994), S. 483-500 
    Details
    ISSN: 1572-8927
    Keywords: Thermodynamics ; kinetics ; chemical relaxation ; temperature-jump ; amplitudes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Amplitudes of chemical relaxation signals can provide useful information as to the thermodynamics of coupled chemical reactions. The temperature-jump technique has been used to investigate the thermodynamic behavior of the Nickel(II)-3,5-dinitrosalicylate system in buffer solution, where complex formation steps are coupled to proton transfer steps. The analysis of the relaxation curves is based on the transformation of a set of coupled elementary reactions into a set of uncoupled ‘normal reactions.’ By analogy with classical titrations, the experiments have been performed by changing the metal ion concentration at constant ligand concentration and pH. Each measured amplitude is associated in this way to a point of a ‘dynamic titration’ and a procedure is formulated by which the values of the equilibrium constants and enthalpies of the normal reactions are simultaneously obtained by simple linear plots. From the dependence of these parameters on suitable functions of the concentrations of the reactants the values of ΔG° and ΔH° of the individual steps are derived. It is shown that the addition of a buffer (instead of an indicator) influences the stoichiometric coefficients of the normal reaction in such a way that measurable amplitudes are produced in systems that, as the presently investigated, in unbuffered solution would remain insensitive to the external perturbation. The circumstances under which the dynamic method offers advantages over the classical techniques are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00972614
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  • 3
    Electronic Resource
    Electronic Resource
    Kinetics and mechanisms of the low-temperature degradation of cellulose (1994)
    Springer
    Cellulose 1 (1994), S. 26-56 
    Details
    ISSN: 1572-882X
    Keywords: low-temperature degradation ; kinetics ; mechanisms ; electrical insulation ; transformers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A critical review is given of the degradation of cellulose in the low-temperature region (below about 300°C) of power transformer operation. The large number of kinetic studies, under a variety of environmental conditions from Kraft paper in insulating oil, to cotton and paper in oxygen, are considered in terms of a first-order polymer chain scission model. In many cases, the data are replotted to suit the model. A common activation energy of 111±6 kjmol−1 is calculated and it is shown that the pre-exponential factor, rather than the activation energy, is sensitive to the oxidizing nature of the environment and the susceptibility to degradation of the material. The chemical mechanisms of degradation are reviewed, and conclusions and recommendations are made regarding chemical condition monitoring and life prediction of electrical insulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00818797
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  • 4
    Electronic Resource
    Electronic Resource
    Oxidation of carbidic carbon on a rhodium surface (1994)
    Springer
    Catalysis letters 27 (1994), S. 79-90 
    Details
    ISSN: 1572-879X
    Keywords: kinetics ; carbon ; oxygen ; recombination ; rhodium ; surface characterisation ; XPS ; AES
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Different mechanisms of atomic carbon and oxygen recombination on a rhodium surface are studied with Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The kinetics of adsorbed carbidic carbon oxidation (carbon coverageθ c ≈ 0.1–0.3 ML) by gas-phase oxygen that proceeds by a Langmuir-Hinshelwood reaction mechanism, provides the value of the activation energy for recombination (E rec ⇂t ≈ 170±20 kJ/mol).E rec ⇂t depends slightly on the carbon coverage. An Eley-Rideal type of reaction was observed for adsorbed oxygen and atomic gas-phase carbon recombination which occurs in a dynamic regime. The low value found for the activation energy (near zero) is consistent with the mechanism that this exothermic reaction is too fast for energy dissipation into the substrate; the energy is mainly transferred into translational, vibrational and rotational energy of CO.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806980
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  • 5
    Electronic Resource
    Electronic Resource
    Dynamics and self-organization of catalytic systems (1994)
    Springer
    Topics in catalysis 1 (1994), S. 305-314 
    Details
    ISSN: 1572-9028
    Keywords: non-Langmuir ; kinetics ; non-linear dynamics ; oscillations ; chaos ; self-organization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of a catalytic reaction is frequently formulated in terms of simple concepts of the Langmuir type. Apart from limitations arising from the non-uniformity of the catalyst's surface and from the coverage dependence of the rate “constants”, several other complications may come into play. These may arise on the “quantum level” where energy flow between the various degrees of freedom may cause failure of simple transition state theory, as well as on the “continuum level” where formulation of rate equations in terms of coupled non-linear differential equations may give rise to a rich scenario of spatio-temporal self-organization, including kinetic oscillations, chaos, and formation of concentration patterns. Several of these phenomena are illustrated by selected examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01492284
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  • 6
    Electronic Resource
    Electronic Resource
    The influence of sulfur dioxide on propane oxidation activity over supported platinum and palladium (1994)
    Springer
    Catalysis letters 30 (1994), S. 41-51 
    Details
    ISSN: 1572-879X
    Keywords: propane ; oxidation ; platinum ; palladium ; sulfur dioxide ; alumina ; zirconia ; activity ; acidity ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Earlier studies have shown that sulfur dioxide and metal-support interaction can strongly influence propane oxidation over platinum. In particular, oxidation activity is enhanced when platinum is supported on sulfated γ-alumina or zirconia compared to γ-alumina. Therefore, it is of interest to compare the performance of palladium under the same experimental conditions. Four model catalysts were examined: Pt/γ-alumina, Pt/zirconia, Pd/γ-alumina and Pd/zirconia. The metal loading was kept at or below 0.05 wt% to emphasize changes in activity attributable to metal-support interaction. Reaction rates were measured with and without sulfur dioxide. Surface sulfation was analyzed by measuring acid strength and evaluating spectra obtained by Fourier-transform infrared spectroscopy. In contrast to platinum, sulfation does not promote propane oxidation on Pd/γ-alumina, and Pd/zirconia is less active than Pd/γ-alumina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00813671
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  • 7
    Electronic Resource
    Electronic Resource
    Spectrophotometric determination of mercury with 5,10,15,20-tetrakis(3-chloro-4-sulfophenyl)porphine by flow injection analysis (1994)
    Springer
    Microchimica acta 113 (1994), S. 81-89 
    Details
    ISSN: 1436-5073
    Keywords: flow injection analysis (FIA) ; mercury ; porphyrin ; kinetics ; spectro-photometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 5,10,15,20-tetrakis(3-chloro-4-sulfophenyl)porphine (m-Cl-TPPS4) was synthesized and used for the Spectrophotometric determination of mercury by flow injection analysis. A pseudo-first-order reaction kinetic mechanism was proposed with a rate constant of 0.8 min−1 for Hg(II) withm-Cl-TPPS4 in the presence of 8-hydroxyquinoline in a medium of 1.0M acetic acid and sodium acetate buffer solution (pH 6.22). In the optimum conditions of reaction temperature (85 ° C), stopped-flow time (60 s) and sampling volume (100 μl), the method's relative standard deviation was 0.82% (n = 12) at 5.0 μg ml−1 mercury, with a linear range of 0–12.0 μg ml−1 and an analytical frequency of 60h−1. The detection limit (3σ) was 0.025 μg ml−1. Interference studies showed that most metal ions co-existing with Hg2+ could be tolerated at 100-fold excess levels, but Zn2+, Cu2+ and Mn2+ needed to be masked. The method has been applied to the analysis of water samples with satisfactory results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01243140
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  • 8
    Electronic Resource
    Electronic Resource
    Slow release rate: Individual granules and population behaviour (1994)
    Springer
    Nutrient cycling in agroecosystems 39 (1994), S. 39-42 
    Details
    ISSN: 1573-0867
    Keywords: Controlled release fertilizers ; kinetics ; mechanism ; nutrient supply ; rate of release ; slow release fertilizers (SRF)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Individual granules within a given granule population of a slow-release fertilizer (SRF) have a different release pattern. The populations studied differed both in relation to the time delay before the start of the release process and to the duration of the release. An association between a short delay period and a rapid release was found. The random reease distribution can be approximated using first-order rate equations. In cases, a term describing a “lag” period should be added. The distribution of release timing among the fertilizer granules may allow a long-lasting nutrient supply to the plant, as long as there are enough granules within the root zone to allow a uniform supply pattern.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00750155
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  • 9
    Electronic Resource
    Electronic Resource
    Comparative studies on species-specific reactivity between renin and angiotensinogen (1994)
    Springer
    Molecular and cellular biochemistry 131 (1994), S. 43-47 
    Details
    ISSN: 1573-4919
    Keywords: angiotensinogen ; kinetics ; recombinant protein ; renin ; species specificity ; transgenic mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The renin-angiotensin system (RAS) is the most important regulator of electrolyte homeostasis and blood pressure. Our recently generated transgenic mice carrying either the human renin (hREN) or human angiotensinogen (hANG) genes did not develop hypertension but dual gene strains obtained by cross-mating separate lines of mice exhibited a chronically sustained increase in blood pressure, suggesting the presence of species-specific reactivity between renin and angiotensinogen. In order to examine this specificity, the present study was designed to perform a strictly comparative study on hydrolysis of hANG by hREN and mouse submandibular renin (mREN)in vitro by using pure proteins. The recombinant hANG (rhANG) and the synthetic human-type tridecapeptide (hTDP), Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Val-Ile-His, corresponding to the N-terminal sequences of hANG, were used to determine the species specificity of recombinant hREN (rhREN) and mREN. While hTDP was cleaved by both rhREN with similar Km and with the same order of kcat, rhANG was cleaved by mREN with 16.7-fold higher Km and with 28.2-fold lower kcat than by rhREN. These results showed that kcat/Km value of mREN for rhANG was 468-fold lower than that for rhREN acting on rhANG.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01075723
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  • 10
    Electronic Resource
    Electronic Resource
    Morphological characteristics of the oxidation of niobium II: The role of stresses on high-temperature morphologies (1994)
    Springer
    Oxidation of metals 41 (1994), S. 235-250 
    Details
    ISSN: 1573-4889
    Keywords: niobium ; oxidation ; morphology ; kinetics ; stresses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of niobium at high temperature (900°C) leads to reaction products with “exotic” morphologies. Morphological and kinetics analysis have been undertaken with Nb platelets. A growth mechanism of the oxide at the edges of the platelet is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01080782
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  • 11
    Electronic Resource
    Electronic Resource
    The effect of purity on high-temperature oxidation of zirconium (1994)
    Springer
    Oxidation of metals 42 (1994), S. 223-237 
    Details
    ISSN: 1573-4889
    Keywords: kinetics ; scale ; oxidation ; zirconium ; purity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation kinetics of zirconium of different purities were studied over the temperature range of 600–1300°C (α- and β-phases). The structure of the oxidized specimens was examined. TGA, XRD, EPMA, SEM, metallographic analysis, and microhardness measurements were carried out. Impurity elements were found to increase the oxidation rate of technical zirconium. The mechanism of the effect of impurity elements on zirconium oxidation was shown to differ for the α- and β-phases. Activation energies were calculated for the parabolic and linear stages of oxidation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01052024
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  • 12
    Electronic Resource
    Electronic Resource
    The effect of purity on the high-temperature oxidation of hafnium (1994)
    Springer
    Oxidation of metals 42 (1994), S. 249-263 
    Details
    ISSN: 1573-4889
    Keywords: kinetics ; scale ; oxidation ; hafnium ; purity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation kinetics of hafnium of different purities were studied in the temperature range of 800–1200°C. This paper concerns the structure studies of the oxidized samples. TGA, XRD, SEM methods, and microhardness measurements were used. Hafnium oxidation follows the parabolic rate law, changing with time to the linear one. Oxidation-reaction products are HfO2(moncl) and α-solid solution of oxygen in hafnium. Anomalous oxidation behavior of hafnium having a high impurity content was found in the range 800–950°C. Activation energies for the parabolic and linear oxidation stages were calculated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01052026
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  • 13
    Electronic Resource
    Electronic Resource
    Enzymology of ADP-ribose polymer synthesis (1994)
    Springer
    Molecular and cellular biochemistry 138 (1994), S. 33-37 
    Details
    ISSN: 1573-4919
    Keywords: poly(ADP-ribose) polymerase ; structure ; chemistry ; kinetics ; automodification ; mechanism(s)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In this minireview, we summarize recent advances on the enzymology of ADP-ribose polymer synthesis. First, a short discussion of the primary structure and cloning of poly(ADP-ribose) polymerase (PARP) [EC 2.4.2.30], the enzyme that catalyzes, the synthesis of poly(ADP-ribose), is presented. A catalytic distinction between the multiple enzymatic activities of PARP is established. The direction of ADP-ribose chain growth as well as the molecular mechanism of the automodification reaction catalyzed by PARP are described. Current approaches to dissect ADP-ribose polymer synthesis into individual reactions of initiation, elongation and branching, as well as a partial mechanistic characterization of the ADP-ribose elongation reaction at he chemical level are also presented. Finally, recent developments in the catalytic characterization of PARP by site-directed mutagensis are also briefly summarized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00928440
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  • 14
    Electronic Resource
    Electronic Resource
    A two-component, non-aqueous route to silica gel (1994)
    Springer
    Journal of sol gel science and technology 2 (1994), S. 35-41 
    Details
    ISSN: 1573-4846
    Keywords: carboxylic acids ; mechanism ; kinetics ; ultrafine porosity ; CO2 adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new means for generating silica gel has been developed. Simple two component systems comprising tetraalkoxysilanes and strong carboxylic acids such as formic acid can react rapidly to give transparent monolithic gels. The acid serves as solvent, water source, and catalyst for both hydrolysis and condensation. Water need not be present as an initial reactant; it is generated in situ during the reaction. The gelation reaction is at least two orders of magnitude faster than those conducted in conventional acid-catalyzed aqueous systems at comparable pH*. Kinetic evidence indicates a lowering of the activation energy of condensation reactions, believed to be associated with reaction of silyl carboxylates and silanol groups. Physical properties of the dry gels such as bulk density more closely resemble conventional acid-catalyzed gels than those associated with other rapidly gelling systems. Dry gels often exhibit porosity so fine that nitrogen (at 77°K) is not absorbed at significant rates. Independent evidence of porosity arises from comparison of skeletal and bulk densities, sample immersion in water and adsorption isotherms of CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00486210
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  • 15
    Electronic Resource
    Electronic Resource
    Substitution of the amino acid at position 102 with polar and aromatic residues influences substrate specificity of lactate dehydrogenase (1994)
    Springer
    The protein journal 13 (1994), S. 129-133 
    Details
    ISSN: 1573-4943
    Keywords: Lactate dehydrogenase ; kinetics ; mutagenesis ; specificity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The Gin residue at amino acid position 102 ofBacillus stearothermophilus lactate dehydrogenase was replaced with Ser, Thr, Tyr, or Phe to investigate the effect on substrate recognition. The Q102S and Q102T mutant enzymes were found to have a broader range of substrate specificity (measured byk cat/K m) than the wild-type enzyme. However, it is evident that either Ser or Thr at position 102 are of a size able to accommodate a wide variety of substrates in the active site and substrate specificity appears to rely largely on size discrimination in these mutants. The Q102F and Q102Y mutant enzymes have low catalytic efficiency and do not show this relaxed substrate specificity. However, their activities are restored by the presence of an aromatic substrate. All of the enzymes have a very low catalytic efficiency with branched chain aliphatic substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01892000
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  • 16
    Electronic Resource
    Electronic Resource
    DEDO: A specific, fluorescent inhibitor for spectroscopic investigations of Na,K-ATPase (1994)
    Springer
    Journal of fluorescence 4 (1994), S. 287-290 
    Details
    ISSN: 1573-4994
    Keywords: Na,K-ATPase ; fluorescent inhibitor ; kinetics ; energy transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The interaction between the fluorescent ouabain derivative DEDO and purified renal Na,K-ATPase (isolated from different animal species) is investigated. Equilibrium binding studies provide a pK value of about 7.5 and a stoichoimetric coefficient of 1. Nonmodified ouabain exhibits the same affinity to the rabbit enzyme; the enzyme originating from the other sources binds DEDO 10 times less strongly than ouabain. Kinetic studies indicate that this is the consequence of a 10 times higher dissociation rate constant of the complexes formed with DEDO. The fluorescence emission intensity of DEDO is enhanced, being dependent on the enzyme source. The single decay time of DEDO is 3 ns in the absence and 21 ns in the presence of the rabbit enzyme and 14 ns in the presence of the pig renal enzyme. This result suggests that the fluorophore of DEDO is bound to a very hydrophobic environment of the enzyme. Further characterization of the static fluorescence spectra provides evidence for energy transfer between Trp residues of the enzyme and DEDO. Distance estimations suggest that one or two Trp residues are likely to be located in the proximity of the fluorophore.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01881441
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  • 17
    Electronic Resource
    Electronic Resource
    Stopped-flow fluorescence studies of the interaction of a mutant form of cytochrome b5 with lipid vesicles (1994)
    Springer
    Journal of fluorescence 4 (1994), S. 227-233 
    Details
    ISSN: 1573-4994
    Keywords: Cytochrome b5 ; site-directed mutagenesis ; kinetics ; fluorescence ; membrane-binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Cytochrome b5 binds spontaneously to lipid vescles and also self-associates in aqueous solution. Two mutant proteins have been generated, one has a self-association constant which is less than that of the native protein, while the other has a larger self-association constant. All three proteins have Trp in the membrane-binding domain but as aqueous solutions of these proteins contain differing amounts of monomeric protein, the kinetics of fluorescence enhancement, when the proteins are mixed with lipid vesicles, are complex. Similar complex kinetics are seen when the Trp are quenched by the addition of bromolipid vesicles. The mutant which has Trp 108 and 112 both replaced by Leu does not self-associate and shows monoexponential stopped-flow fluorescence kinetics. Identical rate constants are seen with this mutant for fluorescence enhancement by POPC and fluorescence quenching by three bromolipids with bromines at the 6,7-, 9,10-, and 11,12-positions of thesn-2 acyl chain. This rate constant is only 1% of the calculated collisional rate constant and it is suggested that the reduced rate is caused by a reduction in the number of productive collisions rather than by a slow rate of penetration of the membrane-binding domain into the bilayer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01878455
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  • 18
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    Kinetics and mechanisms of halide ion catalysis of CO substitution reactions in Os3(CO)12 and Ru3(CO)12 metal carbonyl clusters (1994)
    Springer
    Russian chemical bulletin 43 (1994), S. 1451-1456 
    Details
    ISSN: 1573-9171
    Keywords: metal carbonyl clusters ; osmium, ruthenium, alkynes ; kinetics ; catalytic effect of halide ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The results of kinetic studies on ligand substitution in [M3(CO)11X]− complexes (M = Ru, Os; X = Cl, Br, I) are summarized. The [Os3(CO)11X]− complexes react with PPh3 under mild conditions to initially yield monosubstituted products [Os3(CO)10(PPh3)X]−. The rate of CO substitution obeys a first-order equation with respect to the concentration of the complex and does not depend on the ligand concentration. The rates of the reactions decrease in the order Cl 〉 Br 〉 I withΔH≠ values increasing from 15 to 18 kcal mol−1 and ΔS ≠ values varying from −19 to −13 cal mol−1 K−1. The enhanced reactivities of these complexes as well as the low activation energies and negative activation entropies are discussed in terms of the effects of μ-X bridge formation on the transition state of the reaction. Reactions of PPN[Ru3(CO)11−x (Cl)] (PPN is the bis(triphenylphosphine)iminium cation;x=0, 1) and PPN[Ru3(CO)9(μ3-I)] with alkynes are also reported. The reactivities of alkynes follow the order BuC≡CH ≥ PhC≡CH ≥ EtC≡CEt ≥ PhC≡CPh. The higher rates of the reactions of monosubstituted acetylenes compared with those of their disubstituted analogs are explained by agostic interaction between the metal atom and the C-H bond in the reaction transition state and by steric effects. The results obtained attest that the reaction with alkynes occursvia intermediates containing halide bridges and that μ3-halide complexes are more reactive than μ2-halide complexes.
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    URL: http://dx.doi.org/10.1007/BF00697124
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  • 19
    Electronic Resource
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    Oxidation of organic amide ions by dioxygen (1994)
    Springer
    Russian chemical bulletin 43 (1994), S. 1646-1650 
    Details
    ISSN: 1573-9171
    Keywords: aromatic amines ; amide ions ; oxidation ; dioxygen ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Amide ions generated from secondary aromatic amines with pK a 〉 21 are readily oxidized by dioxygen in the system KOH+18-crown-6+DMSO at room temperature. It was found that the rate limiting stage of the reaction is the interaction of dioxygen with amide ions. The rate of the reaction is determined by two main factors, varying in opposite directions: the degree of ionization of the amine and the reactivity of the amide ions towards dioxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00703478
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  • 20
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    Correlation between solvent-reorganization dynamics and the kinetics of metallotropy in polar media (1994)
    Springer
    Russian chemical bulletin 43 (1994), S. 368-371 
    Details
    ISSN: 1573-9171
    Keywords: kinetics ; solvent dynamics ; radical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of metallotropy of the 3,6-di-tert-butyl-2-(triphenylstannyl)oxyphenoxyl radical has been studied by ESR. The correlation between chemical exchange time τex, solvent polarity, and longitudinal relaxation time of the solvent corresponds to the model of a process controlled by molecular dynamics. A linear relation between τex and correlation time τc for reorientation movements of the radical is found: τex = α · τc. The coefficient α depends on the dielectric properties of the solvent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01169707
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  • 21
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    The Determination of Interfacial Transfer Constants Using Side-by-Side Diffusion Cells (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 1325-1329 
    Details
    ISSN: 1573-904X
    Keywords: interfacial transfer ; partition coefficients ; side-by-side diffusion cells ; kinetics ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A side-by-side diffusion cell setup has been used to determine the pH 7.4 buffer-octanol interfacial transfer constants for twelve compounds. The compounds are a diverse selection of pharmaceuticals, amino acids, and small organics which covers a log distribution coefficient (K) range of −3 to 2. A model based on the resistance summation approach, which deals explicitly with the various barriers involves in the transport process, was used to derive transfer constants from the transport data for each compound. The model gave constants that were well behaved in a published model describing the correlation of the forward and reverse transfer constants to equilibrium K values (r2 = 0.999). These studies demonstrate the utility of side-by-side diffusion cells for the determination of interfacial transfer constants. This type of setup offers the advantages of controlled interfacial area, measurable hydrodynamic effects, and a commercially available apparatus.
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    URL: http://dx.doi.org/10.1023/A:1018954814262
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    Entrapping Efficiency and Drug Release Profile of an Oil-in-Water (o/w) Emulsion Formulation Using a Polydimethylsiloxane-Coated Glass Bead Assay (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 503-507 
    Details
    ISSN: 1573-904X
    Keywords: drug delivery ; emulsion ; entrapping efficiency ; polydimethylsiloxane ; glass beads ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Evaluation of entrapping efficiency is difficult for an o/w emulsion formulation containing a lipophilic oily drug, isocarbacyclin methyl ester (TEI-9090), by commonly employed techniques (dialysis, ultrafiltration, or gel filtration), because of its adsorption to the system materials. Employing this characteristic of TEI-9090, we developed an adsorption technique with polydimethylsiloxane-coated glass beads (PDMS-GB). The assay is based on the quantitative adsorption of unentrapped TEI-9090 to the PDMS-GB. The entrapping efficiency of a 10% soybean oil emulsion containing [3H]TEI-9090 (1 µg/mL) assayed by this method approached 100%. The PDMS-GB assay was performed for the emulsion diluted 100 times with physiological saline at different time intervals after dilution over a period of 24 hr. A plot of [3H]TEI-9090 in the emulsion particles versus time showed rapid release within 1 hr, followed by very slow release, reaching equilibrium. Applying first-order kinetics, the data were found to fit to a biexponential equation over the first hour of release. The terminal release resembled the first-order release of the drug from the phospholipid-rich infranatant, which was separated from the creamy layer by ultracentrifugation of the emulsion and contained 35% [3H]TEI-9090. These results suggest that the drug is released from two components in the emulsion.
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    URL: http://dx.doi.org/10.1023/A:1018902229399
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    Acid-Catalyzed Peptide Bond Hydrolysis of Recombinant Human Interleukin 11 (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 72-76 
    Details
    ISSN: 1573-904X
    Keywords: interleukin 11 (IL-11) ; recombinant human IL-11 ; degradation ; kinetics ; products ; aspartate–proline cleavage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Recombinant human interleukin 11 (rhIL-11) is a multispectrum cytokine that plays an important role in megakaryocytopoiesis and platelet production. Probing rhIL-11 chemical reactivity in aqueous solution is an important initial step in developing a dosage form for rhIL-11 clinical trials. This report documents rhIL-11 degradation kinetics at 50°C in solutions adjusted to pH 3.0 to 9.5. Stressed samples were analyzed by reverse-phase HPLC and degradation product peaks were isolated for structural characterization. The results show maximal stability in the region pH 6.5 to 7.0. Degradation product identification shows that the major reaction pathway in acidic solution involves peptide cleavage at aspartate133–proline134. In alkaline solution, protein disappearance proceeds via nonspecific loss to container surfaces. Degradation products at alkaline pH have not been identified.
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    URL: http://dx.doi.org/10.1023/A:1018945727640
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    Epimerization and Hydrolysis of Dalvastatin, a New Hydroxymethylglutaryl Coenzyme A (HMG-CoA) Reductase Inhibitor (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 165-170 
    Details
    ISSN: 1573-904X
    Keywords: dalvastatin ; hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitor ; epimerization ; hydrolysis ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In aqueous solutions, dalvastatin (1) undergoes epimerization as well as hydrolysis. The transformation of the drug was studied as a function of pH at 25°C in aqueous solutions containing 20% acetonitrile. At all pH values, first-order plots for the conversion are biphasic, indicating rapid equilibration of 1 with its epimer (2) and slower hydrolysis of 1 to the corresponding β-hydroxy acid (3). Apparent first-order rate constants for the biexponential equation are given as a function of pH. The alkyl–oxygen cleavage of the lactone ring results in the epimerization of 1 to 2, whereas the acyl–oxygen cleavage results in the hydrolysis of 1 to 3. The epimerization is an SN1 reaction reaching an equilibrium of [l] eq/[2] eq = 1.27. The epimerization rate is increased with an increase in the water content of the solvent. The hydrolysis of 1 to 3 is acid and base catalyzed. The hydrolysis is reversible in acidic media and irreversible in neutral and basic media. At pH values greater than 9, the hydrolysis reaction proceeds more rapidly than the epimerization.
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    URL: http://dx.doi.org/10.1023/A:1018978602141
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    Entrapping Efficiency of an Oil-in-Water Emulsion Containing Isocarbacyclin Methyl Ester (TEI-9090) in Dog and Human Sera (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 1677-1679 
    Details
    ISSN: 1573-904X
    Keywords: o/w emulsion ; serum ; entrapping efficiency ; kinetics ; SDS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018938627408
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    Is Stability Prediction Possible for Protein Drugs? Denaturation Kinetics of β- Galactosidase in Solution (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 1721-1725 
    Details
    ISSN: 1573-904X
    Keywords: protein drug ; denaturation ; aggregation ; kinetics ; Eyring equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Denaturation and aggregation kinetics of Aspergillus oryzae β-galactosidase in solution were studied in order to determine whether the stability of protein drugs can be predicted. Denaturation of β-galactosidase, monitored by measuring enzyme activity, conformed to first-order kinetics, whereas aggregation of the denatured form, monitored by high performance size exclusion chromatography, showed a reaction order higher than 1. Denaturation of β-galactosidase was irreversible and exhibited a biphasic kinetic pattern which could be explained by assuming that two isoenzymes denatured irreversibly at different rates. Linear Arrhenius plots were obtained for the estimated rate constants, and ΔH
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  • 27
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    Block copolymerization initiated by Mn(III)-poly(ethylene glycol) redox system — general features and kinetics (1994)
    Springer
    Colloid & polymer science 272 (1994), S. 777-783 
    Details
    ISSN: 1435-1536
    Keywords: Mn(III)-poly(ethylene glycol) ; acrylonitrile ; block copolymerization ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The kinetics and mechanism of thermal polymerization of acrylonitrile initiated by Mn(III) pyrophosphate — poly(ethylene glycol) (PEG, molecular weight 6000) redox system in aqueous sulfuric acid medium was studied in the temperature range 30–60°C. The overall rates of polymerization and the disappearance of Mn3+ were determined. The polymerization was initiated by the organic free radical produced from the Mn3+-PEG reaction and the termination was by the metal ions. The rate of polymerization of acrylonitrile was found to be directly proportional to the square of the monomer concentration and first power of PEG concentration, and inversely proportional to the concentration of Mn3+. The rate of manganic ion disappearance was found to be directly proportional to manganic ion concentration and PEG concentration, and independent of the monomer concentration. Based on these observations, a plausible reaction scheme was suggested and suitable kinetic expressions were evaluated.
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    URL: http://dx.doi.org/10.1007/BF00652418
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    Are cell redox or lactate dehydrogenase kinetics responsible for the absence of gluconeogenesis from lactate in sea raven, hepatocytes? (1994)
    Springer
    Fish physiology and biochemistry 13 (1994), S. 59-67 
    Details
    ISSN: 1573-5168
    Keywords: fish ; sea raven ; gluconeogensis ; hepatocytes ; redox ; LDH ; isozymes ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Previous studies have reported very low rates of gluconeogenesis from lactate in sea raven (Hemitripterus americanus) hepatocytes compared to other teleosts studied. This study examines whether hepatic cell redox or lactate dehydrogenase (LDH) characteristics may explain this observation. Sea raven hepatic optimal LDH activities (pyruvate reductase direction) were more than 40 times less compared with rainbow trout liver values (40 vs 1914 μmol·min−1·g−1 protein). The Km(lactate) was 9.24 and 0.86 mM for sea raven and trout hepatic LDH, but the Km(pyruvate) was similar between the two species (0.11 and 0.21 mM, respectively). These results suggested that sea raven liver LDH did not favour lactate use and was more indicative of the mammalian M-isozyme. Gel electrophoresis showed a predominant intermediate isozyme, with a small amount of the M-type LDH. Phosphoenolpyruvate carboxykinase (PEPCK) was localized to the mitochondrial compartment, while there was no apparent mitochondrial glutamate-oxaloacetate transaminase (GOT) activity. No in vitro lactate flux to glucose was found in untreated, 10 mM ethanol-treated, or 3 mM NH4Cl-treated sea raven hepatocytes, although CO2 production from lactate was decreased by ethanol and increased by NH4Cl. These results provide evidence that cell redox does not limit gluconeogenesis from lactate, while low activities and the kinetic characteristics of LDH may partially explain the low lactate gluconeogenesis reported in sea raven hepatocytes.
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    URL: http://dx.doi.org/10.1007/BF00004120
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    Morphological responses of the rainbow trout (Oncorhynchus mykiss) gill to hyperoxia, base (NaHCO3) and acid (HCl) infusions (1994)
    Springer
    Fish physiology and biochemistry 12 (1994), S. 465-477 
    Details
    ISSN: 1573-5168
    Keywords: fish ; chloride cell ; morphology ; kinetics ; Km ; Jmax ; acid-base
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Marked morphological responses occur in the gills of freshwater rainbow trout in response to experimental acid-base disturbance and these responses play an important role in acid-base correction. Compensated respiratory acidosis induced by 70h exposure to environmental hyperoxia (elevated water PO2) caused a 33% decrease in branchial chloride cell fractional surface area (CCFA). Metabolic alkalosis induced by normoxic recovery (6h) from hyperoxia (72h) caused a 50% increase in CCFA, whereas metabolic alkalosis induced by infusion (19h) of NaHCO3 caused a 70% rise. However, the largest increase (135%) in CCFA was seen in response to infusion (19h) of HCl. NaCl infusion had no effect. A particular goal was to assess the relative importance of changes in CCFA vs. changes in internal substrate (HCO3 −) availability in regulating the activity of the branchial Cl−/HCO3 − exchange system. For each of the experimental treatments, the accompanying blood acid-base status and branchial transport kinetics (Km, Jmax) for Cl− uptake had been determined in earlier studies. In the present study, a positive linear relationship was established between CCFA and JCl− max in individual control fish in the absence of an acid-base disturbance. By reference to this relationship, observed changes in JCl− max during metabolic acid-base disturbances were clearly due to changes in both CCFA and internal substrate levels (plasma [HCO3 −]) with the two factors having approximately equal influence.
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    Transport of calcium by mitochondria (1994)
    Springer
    Journal of bioenergetics and biomembranes 26 (1994), S. 471-485 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; transport ; calcium ; metabolic mediator ; kinetics ; calcium pulses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The identification of intramitochondrial free calcium ([Ca2+ m) as a primary metabolic mediator [see Hansford (this volume) and Gunter, T. E., Gunter, K. K., Sheu, S.-S., and Gavin, C. E. (1994)Am. J. Physiol. 267, C313–C339, for reviews] has emphasized the importance of understanding the characteristics of those mechanisms that control [Ca2+]m. In this review, we attempt to update the descriptions of the mechanisms that mediate the transport of Ca2+ across the mitochondrial inner membrane, emphasizing the energetics of each mechanism. New concepts within this field are reviewed and some older concepts are discussed more completely than in earlier reviews. The mathematical forms of the membrane potential dependence and concentration dependence of the uniporter are interpolated in such a way as to display the convenience of consideringV max to be an explicit function of the membrane potential. Recent evidence for a transient rapid conductance state of the uniporter is discussed. New evidence concerning the energetics and stoichiometries of both Na+-dependent and Na+-independent efflux mechanisms is reviewed. Explicit mathematical expressions are used to describe the energetics of the system and the kinetics of transport via each Ca2+ transport mechanism.
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    The effects of flow rate and distance travelled on the mobility of phosphate in soils (1994)
    Springer
    Transport in porous media 16 (1994), S. 237-251 
    Details
    ISSN: 1573-1634
    Keywords: phosphate ; soil ; adsorption ; leaching ; kinetics ; computer simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Effects of flow rate and distance travelled on average mobilities of phosphate in a soil are estimated from breakthrough curves of phosphate at the outlets of small columns of soil, following step increases in the concentration at the inlets. Experimental results are compared with results from a computer simulation model of leached columns of soil. Average mobilities of phosphate in columns of soil, following a step increase in the input concentration, decrease with decreasing rate of flow and with increasing distance travelled and appear to be linearly correlated on a logarithmic scale with both flow rate and distance travelled. An empirical equation, describing these relationships, is fitted to data from leaching experiments at flow rates between 30 and 600 cm/day in ≈ 10 cm long columns of soil. Coefficients are obtained by curve fitting breakthrough curves, calculated with a numerical computer simulation model, to experimental breakthrough curves. The fitted equation enables extrapolation to flow rates and travel distances that are more relevant to a field situation.
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    The isothermal crystallization of engineering polymers — POM and PEEK (1994)
    Springer
    Colloid & polymer science 272 (1994), S. 1-16 
    Details
    ISSN: 1435-1536
    Keywords: Polymer crystallization ; kinetics ; modeling ; POM ; PEEK
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The isothermal crystallization of two engineering polymers — POM and PEEK — was studied, both theoretically and experimentally. The experiments were performed by means of differential scanning calorimetry (DSC) and polarized light optical microscopy (OM). Building on previously developed theoretical formalisms (Avrami/Evans, Hillier and Tobin), a new procedure is presented, based on Tobin's model coupled with a modification of Hillier's calculation technique, to accurately describe the kinetics and mechanism of the crystallization of polymers from quiescent melts. First, it is shown that Tobin's model alone, without modification, is more accurate than Avrami/Evans model to describe single-mechanism processes, for a wide range of materials and for longer crystallization times, despite having exactly the same nature and number of parameters (the kinetic, nucleation and growth rate-related, parameterK and the dimensionalityn). Then, Hillier's formalism is modified and combined with Tobin's model, to accurately predict the kinetics of dual mechanism crystallization processes; a clear contrast is drawn with Hillier's Avrami-based, original procedure which uses the same number and nature of parameters, but cannot adequately predict the experimental behavior. The parameter values predicted by the model(s) and procedure presented in this work are all given, are then physically interpreted and, in the case of POM, related to independent morphological observations by polarized light optical microscopy. They are also consistent with electron microscopy observations made by other authors on the detailed morphology of the spherulitic crystallization of polymers.
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    The kinetics of reactions around the cytochrome bf complex studied in an isolated system (1994)
    Springer
    Photosynthesis research 40 (1994), S. 199-206 
    Details
    ISSN: 1573-5079
    Keywords: cytochrome bf complex ; electron transfers ; kinetics ; quinol oxidation ; Q-cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The kinetics of oxidation and reduction of P700, plastocyanin, cytochrome f and cytochrome b-563 were studied in a reconstituted system consisting of Photosystem I particles, cytochrome bf complex and plastocyanin, all derived from pea leaf chloroplasts. Decyl plastoquinol was the reductant of the bf complex. Turnovers of the system were initiated by laser flashes. The reaction between oxidised P700 and plastocyanin was non-homogeneous in that a second-order rate coefficient of c. 5×10−7 M−1 s−1 applied to 80% of the P700+ and c. 0.7×107 M−1 s−1 to the remainder. In the presence of bf complex, but without quinol, the electron transfer between cytochrome f and oxidised plastocyanin could be described by a second-order rate coefficient of c. 4×107 M−1 s−1 (forward), and c. 1.6×107 M−1 s−1 (reverse). The equilibrium coefficient was thus 2.5. Unexpectedly, there was little reduction of cytochrome f + or plastocyanin+ by electrons from the Rieske centre. With added quinol, reduction of cytochrome b-563 occurred. Concomitantly, electrons appeared in the oxidised species. It was inferred that either the Rieske centre was not involved in the high-potential chain of electron transfer events, or that, only in the presence of quinol, electrons were quickly passed from the Rieske centre to cytochrome f +. Additionally, the presence of quinol altered the equilibrium coefficient for the cyt f/PC interaction from 2.5 to c. 5. The reaction between quinol and the bf complex was describable by a second-order rate coefficient of about 3×106 M−1 s−1. The pattern of the redox reactions around the bf complex could be simulated in detail with a Q-cycle model as previously found for chloroplasts.
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    Degradation of the Antiarthritic Prodrug, 3-Carboxy-5-methyl-N-[4-(trifluoromethoxy)phenyl]-4-isoxazolecarboxamide, in Aqueous Solution (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 345-348 
    Details
    ISSN: 1573-904X
    Keywords: kinetics ; decarboxylation ; leflunomide ; deacetylation ; dissociation constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018940415770
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    Growth characteristics of Geotrichum ingens on propionic acid and acetic acid in batch and continuous culture (1994)
    Springer
    World journal of microbiology and biotechnology 10 (1994), S. 505-509 
    Details
    ISSN: 1573-0972
    Keywords: Acetic acid ; chemostat ; Geotrichum ingens ; growth ; inhibition ; kinetics ; monocarboxylic acids ; propionic acid ; yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Growth of Geotrichum ingens in batch cultures was completely inhibited by 47 g acetic acid/l or 33 g propionic acid/I. With mixtures of acetic and propionic acids, however, growth only ceased at 55 g/l. Acetic acid inhibited growth linearly, whereas propionic acid inhibited growth non-linearly. In continuous culture, two steady states at each dilution rate were observed at high dilution rates for acetic acid and propionic acid. The highest yield coefficient (0.69 g cells/g substrate) was achieved with propionic acid as substrate. On both substrates and their mixtures, the protein content of the biomass increased when the dilution rate was increased.
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    Thermal decomposition of 1-ethyl-5-iodotetrazole (1994)
    Springer
    Russian chemical bulletin 43 (1994), S. 1812-1815 
    Details
    ISSN: 1573-9171
    Keywords: kinetics ; mechanism ; thermolysis ; 1-ethyl-5-iodotetrazole ; mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal decomposition of 1-ethyl-5-iodotetrazole in a melt and in solutions was studied using thermogravimetry, manometry, pyrolytic mass spectrometry, and IR spectroscopy. The kinetic and activation parameters of the process and the nature of the decomposition products were determined. The reaction mechanism is assumed to involve equilibrium tautomeric rearrangement of the tetrazole to azidoazomethine form followed by homolytic cleavage of the C-I bond.
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    URL: http://dx.doi.org/10.1007/BF00696307
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    Effect of the nature of the cation in 2,6-di-tert-pentylphenolates on the kinetics and mechanism of the reaction of 2,6-di-tert-pentylphenol with methyl acrylate (1994)
    Springer
    Russian chemical bulletin 43 (1994), S. 769-773 
    Details
    ISSN: 1573-9171
    Keywords: 2,6-di-tert-pentylphenol, methyl acrylate, Na and K cations ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The nature of the cation (K or Na) in 2,6-di-tert-pentylphenolates (ArOK or ArONa) affects the kinetics of the reaction of 2,6-di-tert-pentylphenol (ArOH) with methyl acrylate. This is associated with the ability of ArONa to replace the cation with a proton during interaction with methyl 3-(4-hydroxy-3,5-di-tert-pentylphenyl)propionate (HOArAlkOMe) to form a more efficient catalyst, sodium 4-(2-methoxycarbonylethyl)-2,6-di-tert-pentylphenolate (NaOArAlkOMe). Two different kinetic schemes, which describe the kinetics of the consumption of ArOH in the presence of ArOK and ArONa, are proposed. The elemental-stage rate constants are calculated by mathematical simulation of the reaction kinetics with consideration of the features of catalysis in the presence of ArOK and ArONa.
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    URL: http://dx.doi.org/10.1007/BF00717335
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