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  • Articles: DFG German National Licenses  (247)
  • 1995-1999  (247)
  • 1980-1984
  • 1998  (247)
  • Industrial Chemistry and Chemical Engineering  (141)
  • Nuclear reactions
  • Physical Chemistry
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  • Articles: DFG German National Licenses  (247)
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  • 1995-1999  (247)
  • 1980-1984
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Space science reviews 84 (1998), S. 199-206 
    ISSN: 1572-9672
    Keywords: Nuclear reactions ; Nucleosynthesis ; Abundances ; Stars:Evolution ; Interior ; Rotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We first recall the observational and theoretical facts that constitute the so-called 3He problem. We then review the chemical anomalies that could be related to the destruction of 3He in red giants stars. We show how a simple consistent mechanism can lead to the destruction of 3He in low mass stars and simultaneously account for the low 12C/13C ratios and low lithium abundances observed in giant stars of different populations. This process should both naturally account for the recent measurements of 3He/H in galactic HII regions and allow for high values of 3He observed in some planetary nebulae. We propose a simple statistical estimation of the fraction of stars that may be affected by this process.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The apparent rate constants of formation (k1) and hydrolysis (k2) of the Schiff bases formed between pyridoxal and polyallylamine has been fitted to a kinetic scheme that involve the different protonated species in the reaction medium and the individual rate constants of formation (k1i) and hydrolysis (k2i). The (k1i) values precludes an acid catalyzed intramolecular process. The effects of hydrophobic medium due to the presence of the macromolecule on the reaction is also discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 1-6, 1998.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 21-29 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas-phase reaction of ozone with a series of unsaturated oxygenates and with 1-pentene has been studied at ambient T (287-296 K) and p=1 atm. of air. Reaction rate constants, in units of 10-18 cm3 molecule-1 s-1, are 0.22±0.05 for 2 (5H)-furanone, 1.08±0.20 for methacrolein, 1.74±0.20 for crotonaldehyde, 5.84±0.39 for methylvinyl ketone, 1.05±0.15 for methyl acrylate, 3.20±0.47 for vinyl acetate, 59.0±8.7 for cis-3-hexenyl acetate, 154±30 for ethylvinyl ether, ≥(315±23) for linalool, and 10.9±1.4 for 1-pentene. The results are compared to literature data for the compounds studied and for other unsaturated oxygenates, and are discussed in terms of reactivity toward ozone as a function of the nature, number, and position of the oxygen-containing substituents (SINGLEBOND)CHO, (SINGLEBOND)C(O)R, (SINGLEBOND)C(O)OR, and (SINGLEBOND)OC(O)R. Atmospheric implications are briefly examined. © 1998 John Wiley & Sons, Inc. Int. J Chem Kinet: 30: 21-29, 1998.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 55-61 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tartaric acid oxidation by vanadium(V) in sulfuric acid medium was investigated spectrophotometrically at 760 nm and 30°C by appearance of the vanadium(IV), as vanadyl. The reaction rate was determined under pseudo-first-order conditions with an excess of hydroxyacid over the oxidant concentration. The oxidation showed a first-order dependence with respect to vanadium(V) concentration and fractional orders with respect to tartaric acid and sulfuric acid concentrations, with no control and with constant ionic strength. The reaction rate is enhanced by an increase of ionic strength, and slightly reduced by a decrease of the dielectric constant of the medium. The activation parameters were calculated based on the rate constants determined in the 293 to 313 K interval. The proposed oxidation mechanisms and the derived rate laws are consistent with the experimental rate laws. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 55-61, 1998.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 99-110 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanism of silane thermal decomposition is investigated in a flow reactor. The time dependencies of silane consumption and disilane formation were compared with those parameters of solid product (aerosol particles) such as concentration, total hydrogen content in solid product, and fraction of hydrogen contained in solid product as polyhydride groups (SiH2)n. Silane loss and gaseous product formation were analyzed using a mass spectrometer. The hydrogen content in solid product was analyzed by the methods of IR-spectroscopy and hydrogen evolution. Based on a simple kinetic scheme we qualitatively explained the experimental dependencies of silane conversion and disilane formation, the effective activation energy of the decomposition process, and the amount of polyhydride groups in the solid product on reaction time and initial silane concentration. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 99-110, 1998.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 137-143 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of tert-amyl methyl ether (TAME) from methanol (MeOH) and tert-amyl alcohol (TAA) in the liquid phase was studied by using an ion exchange resin, Amberlyst15 (A15) in the H+ form. Experiments were carried out in a stirred batch reactor under atmospheric pressure. The effects of catalyst size, agitation speed, temperatures, feed ratio and water on the reaction rate were investigated. Both of intraparticle and external diffusion effects could be neglected in this system. The dehydration of TAA could be decreased by increasing the ratio of MeOH/TAA and the reaction rates were greatly inhibited by water.A kinetic model which considered the inhibition of water was proposed. The experimental results agreed well with the model. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 137-143, 1998.
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  • 7
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of proton transfer between poly(A - AH) (partially protonated double-stranded polyadenylic acid) and CPR (chlorophenol red), and between poly(C - H - C) (partially protonated double-stranded polycytidylic acid) and the indicators CPR, BCP (bromocresol purple), and BCG (bromocresol green) have been investigated at 25°C and ionic strength 0.1 M (NaClO4) by the temperature-jump method. The acidic proton of poly(C - H - C) is engaged in a hydrogen bond (N3H+----N3) which is believed to contribute to stabilizing the double-strand conformation, whereas the acidic proton of poly(A - A - H) does not form hydrogen bonds. The analysis of the dependence of the relaxation times on the concentrations of the reactants has enabled the evaluation of the rate constants for the direct proton transfer and for the protolysis paths. The rate constants for proton recombination with the deprotonated forms of the polynucleotides and the indicators are of the order of magnitude expected for diffusion controlled processes involving oppositely charged ions (k2=(0.2-1.6)×1010 M-1s-1). The direct proton transfer from poly(C - H - C) to BCG is thermodynamically disfavored and its rate constant, k1, is lower than k2 by about three orders of magnitude. The (thermodynamically favored) proton transfers from poly(A - A - H) to CPR and from poly(C - H - C) to CPR and BCP are characterized by similar values of k1. This result indicates that the hydrogen bonds in poly(C - H - C) are very weak and suggests that the stabilization of the double-stranded conformation of this polynucleotide could be ascribed to the large number of hydrogen bonds rather than to their specific strength. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 161-169, 1998.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 201-206 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dual-phase oscillations are observed in Belousov-Zhabotinsky system with 4-hydroxy-3-methoxybenzaldehyde (vanillin) as the substrate and manganous sulphate or ammonium Ce(IV) sulphate as the catalyst. The nonoscillatory period of time between the two phases decreases with increase in the concentration of the catalyst and the substrate. Under uncatalyzed and ferroin catalyzed conditions the system exhibits single-phase oscillations. The first-phase oscillations are due to vanillin whereas the second-phase oscillations are brought about by 4-hydroxy-3-methoxybenzoic acid (vanillic acid) formed during the course of the first-phase reactions. The reactions are explained with relevant steps of the FKN mechanism. © 1998 John Wiley & Sons, Inc. Int J. Chem. Kinet 30: 201-206, 1998.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 215-221 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The lifetime of the ferryl ion FeO2+, (minutes at pH below 1) is reduced by a factor of 50 at pH above 3. This is rationalized in terms of an acid-base equilibrium between two different hydrolytic forms of this species (Fe(OH)++2 and Fe(OH)+3) with a pKa=2.0. The rate constants for reactions between FeO2+ and selected compounds found in cloud water were measured in acid solutions by stopped-flow technique. For inorganic reactants: kHNO2=1.1×104 M-1 s-1, kNO2-≤105 M-1 s-1, kCl-=1.0×102 M-1 s-1, kHSO3-=2.5×105 M-1 s-1, kSO2=4.5×105 M-1 s-1, and kMn(II)=1.0×104 M-1 s-1 were obtained and for the organic reactants: kHCOOH=160 M-1 s-1, kHCOO-=3×105 M-1, kCH3COOH=3.1 M-1 s-1, kCH2(OH)2=400 M-1 s-1, kCH3COCH3=16 M-1 s-1, kCH3CH20H=2.5×103 M-1 s-1, kC6H5OH=4.0×103 M-1 s-1, and kC6H5COOH=80 M-1 s-1 were obtained. A good correlation between log(k) and the standard one electron reduction potential (E°) indicates that the reactions of inorganic compounds proceed by electron transfer. The reaction mechanisms in case of organic compounds are very similar to the reactions of the OH radical, i.e., H-abstraction, and a fairly good correlation between log(k) and the bond dissociation energy BDE was obtained. Activation parameters were measured for the reaction of FeO2+ with HNO2 (Ea=34.5 kJ/mol); Mn2+ (Ea=21.3 kJ/mol); HCOOH (Ea=22.3 kJ/mol); CH2(OH)2 (Ea=44.5 kJ/mol); and C6H5OH (Ea=28.1 kJ/mol). © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 215-221, 1998.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 249-255 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A discharge flow reactor coupled to a laser-induced fluorescence (LIF) detector and a mass spectrometer was used to study the kinetics of the reactions CH3O+Br→products (1) and CH3O+BrO→products (2). From the kinetic analysis of CH3O by LIF in the presence of an excess of Br or BrO, the following rate constants were obtained at 298 K: k1=(7.0±0.4)×10-11 cm3 molecule-1 s-1 and k2=(3.8±0.4)×10-11 cm3 molecule-1 s-1. The data obtained are useful for the interpretation of other laboratory studies of the reactions of CH3O2 with Br and BrO. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 249-255, 1998.
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  • 11
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 471-474 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a relative rate method, rate constants have been measured for the gas-phase reactions of the OH radical with the dibasic esters dimethyl succinate [CH3OC(O)CH2CH2C(O)OCH3], dimethyl glutarate [CH3OC(O)CH2CH2CH2C(O)OCH3], and dimethyl adipate [CH3OC(O)CH2CH2CH2CH2C(O)OCH3] at 298±3 K. The rate constants obtained were (in units of 10-12 cm3 molecule-1 s-1): dimethyl succinate, 1.4±0.6; dimethyl glutarate, 3.3±1.1; and dimethyl adipate, 8.4±2.5, where the indicated errors include the estimated overall uncertainty of ±25% in the rate constant for cyclohexane, the reference compound. The calculated tropospheric lifetimes of these dibasic esters due to gas-phase reaction with the OH radical range from 1.4 days for dimethyl adipate to 8.3 days for dimethyl succinate for a 24 h average OH radical concentration of 1.0×106 molecule cm-3. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 471-474, 1998
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  • 12
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of mixed CH3CN(SINGLEBOND)H2O solvents on rates of aminolysis of ionized phenyl salicylate, PS-, reveal a nonlinear decrease in the nucleophilic second-order rate constants, knms, (for aminolysis) with increase in the content of CH3CN until it becomes ∼50%, v/v. The values of knms remain almost unchanged with change in the CH3CN content within 50 to 70 or 80%, v/v. The effects of mixed CH3CN(SINGLEBOND)H2O solvents on pKa of leaving group, phenol, and protonated amine nucleophile have been concluded to be the major source for the observed mixed solvent effects on knms. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 301-307, 1998.
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  • 13
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 629-640 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article describes an experimental and modeling study of the oxidation of isobutene. The low-temperature oxidation was studied in a continuous-flow stirred-tank reactor operated at constant temperature (from 833 to 913 K) and pressure (1 atm), with fuel equivalence ratios from 3 to 6 and space times ranging from 1 to 10 s corresponding to isobutene conversion yields from 1 to 50%. The main carbon containing products were analyzed by gas chromatography. The ignition delays of isobutene-oxygen-argon mixtures with fuel equivalence ratios from 1 to 3 were measured behind shock waves. Reflected shock waves permitted to obtain temperatures from 1230 to 1930 K and pressures from 9.5 to 10.5 atm.A mechanism has been proposed to reproduce the profiles obtained for the reactants consumption and the products formation during the slow oxidation and to compute the ignition delays in the shock tube. Simulations were performed using CHEMKIN II. A correct agreement between the simulated values and the experimental data has been obtained in both apparatuses. The main reaction paths have been determined for both series of measurements by a sensitivity and rate of production analysis. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 629-640, 1998
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  • 14
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 589-594 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a relative rate method, rate constants for the gas-phase reactions of 2-methyl-3-buten-2-ol (MBO) with OH radicals, ozone, NO3 radicals, and Cl atoms have been investigated using FTIR. The measured values for MBO at 298±2 K and 740±5 torr total pressure are: kOH=(3.9±1.2)×10-11 cm3 molecule-1 s-1, kO3=(8.6±2.9)×10-18 cm3 molecule-1 s-1, kNO3=(8.6±2.9)×10-15 cm3 molecule-1 s-1, and kCl=(4.7±1.0)×10-10 cm3 molecule-1 s-1. Atmospheric lifetimes have been estimated with respect to the reactions with OH, O3, NO3, and Cl. The atmospheric relevance of this compound as a precursor for acetone is, also, briefly discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 589-594, 1998
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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 621-628 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,1,1-Trifluoroethane has been decomposed in comparative rate single-pulse shock-tube experiments. The rate expression for elimination at ca. 2.5 bar and in the temperature range of 1050 to 1200 K has been found to be\documentclass{article}\pagestyle{empty}\begin{document}$ \it k\rm (CF_{3}\joinrel{\relbar\!\!\relbar}CH_{3}\relbar\!\!\rightarrow HF+CF_{2}=CH_{2})=7.0\times 10^{14}\ exp(-37260/T)s^{-1} $\end{document}The experimental conditions appear to be such that the unimolecular reaction is at the beginning of the fall-off region and we find that for step sizes down between 500 and 1000 cm-1 the high-pressure rate expression is in the range\documentclass{article}\pagestyle{empty}\begin{document}$ \it k\rm (CF_{3}\joinrel{\relbar\!\!\relbar}CH_{3}\relbar\!\!\rightarrow HF+CF_{2}=CH_{2})=2.0\times 10^{15}\ exp(-38300/T)\ to\ 4\ \times\ 10^{15}\ exp(-39000/T)s^{-1} $\end{document}where the smaller rate parameters refer to the larger step size down. The results are compared with those from an earlier study and the anomalously high A-factor is noted. It is suggested that the existing rate expressions for the fluorinated ethanes may need to be reevaluated. © 1998 John Wiley & Sons, Inc., Int J Chem Kinet: 30: 621-628, 1998
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 673-681 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The authors present a critical analysis of the use of an overall single reaction rate equation instead of the true rate equations corresponding to the decomposition of a substance according to two parallel reactions. Isothermal as well as nonisothermal decomposition are considered. An apparent compensation effect has been evidenced in both cases. It has been assigned to the dependence of the kinetic parameters on temperature (for the isothermal case), conversion, and heating rate (for nonisothermal one). © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 673-681, 1998
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  • 17
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 785-797 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reduction of iodine by hydroxylamine within the [H+] range 3×10-1-3×10-4 mol.L-1 was first studied until completion of the reaction. In most cases, the concentration of iodine decreased monotonically. However, within a narrow range of reagent concentrations ([NH3OH+]0/[I2]0 ratio below 15, [H+] around 0.1 mol.L-1, and ionic strength around 0.1 mol.L-1), the [I2] and [I3-] vs. time curves showed 2 and 3 extrema, respectively. This peculiar phenomenon is discussed using a 4 reaction scheme (I2+I-⇔I3-, 2 I2+NH3OH++H2O→HNO2+4 I-+5 H+, NH3OH++HNO2→N2O+2 H2O+H+, and 2 HNO2+2 I-+2 H+→2 NO+I2+2 H2O). In a flow reactor, sustained oscillations in redox potential were recorded with an extremely long period (around 24 h).The kinetics of the reaction was then investigated in the starting conditions. The proposed rate equation points out a reinforcement of the inhibition by hydrogen ions when [H+] is above 4×10-2 mol.L-1 at 25°C. A mechanism based on ion-transfer reactions is postulated. It involves both NH2OH and NH3OH+ as the reducing reactive species. The additional rate suppression by H+ at low pH would be connected to the existence of H2OI+ in the reactive medium. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 785-797, 1998
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  • 18
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some relative rate experiments have been carried out at room temperature and at atmospheric pressure. This concerns the OH-oxidation of some oxygenated volatile organic compounds including methanol (k1), ethanol (k2), MTBE (k3), ethyl acetate (k4), n-propyl acetate (k5), isopropyl acetate (k6), n-butyl acetate (k7), isobutyl acetate (k8), and t-butyl acetate (k9). The experiments were performed in a Teflon-film bag smog chamber. The rate constants obtained are (in cm3 molecule-1 s-1): k1=(0.90±0.08)×10-12; k2=(3.88±0.11)×10-12; k3=(2.98±0.06)×10-12; k4=(1.73±0.20)×10-12; k5=(3.56±0.15)×10-12; k6=(3.97±0.18)×10-12; k7=(5.78±0.15)×10-12; k8=(6.77±0.30)×10-12; and k9=(0.56±0.11)×10-12. The agreement between the obtained rate constants and some previously published data has allowed for most of the studied compounds to point out a coherent group of values and to suggest recommended values. Atmospheric implications are also discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 839-847, 1998
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  • 19
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetic studies of the oxidation of the bis[1-hydroxy-2-(salicylideneamino)ethane]manganese(II) complex by hydrogen peroxide in acetonitrile solutions, at (30.0±0.2)°C, are described. A first-order dependence on the total manganese and the peroxide concentrations was verified, leading to the rapid formation of a Mn(III) intermediate, monitored by stopped-flow measurements, at 394 nm, with a rate constant kf=(1.15±0.03)×105 mol-1 dm3 s-1. The participation of hydroxyl radicals in the process was detected by spin-trapping EPR spectra. The final product was monitored both by EPR spectra, and spectrophotometrically by the slow decay of the intermediary Mn(III) species, with a rate constant kd=(2.60±0.09) s-1. It was identified as the corresponding mononuclear Mn(IV) complex, and characterized by different spectroscopic techniques. Comparative results of the reactivity of the starting complex versus molecular oxygen, leading to the same final product, were also discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 889-897, 1998
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  • 20
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 923-932 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of 1-butanethiol with hydrogen atoms was investigated at room temperature under pressures of 133, 266, 532, 2660, and 5320 Pa, using two types of fast-flow discharge reactors; the main products were n-butane and 1-butene with total yields of more than 90%. In the reaction of 1-butanethiol and deuterium atoms, monodeuterated 1-butanethiol was observed by a photo-ionizing mass spectrometer. The relative rate of the two initial reactions of 1-butanethiol with hydrogen atoms was 0.272 (k1/k2). The n-butane and 1-butene are considered to be produced via chemically activated 1-butanethiol on the basis of the pressure dependence of the two main products.\scriptfont4=\seveni \scriptscriptfont4=\fivei \halign{\hfill $#$&$#$\hfill &$#$\hfill &\hfill\qquad\qquad #\cr\rm 1\hbox{-}C_{4}H_{9}S&\rm H&\rm +H\longrightarrow 1\hbox{-}C_{4}H_{9}\cdot +H_{2}S& (1)\cr \rm 1\hbox{-}C_{4}H_{9}S&\rm H&\rm +H\longrightarrow 1\hbox{-}C_{4}H_{9}S\cdot +H_{2}& (2)\cr\rm 1\hbox{-}C_{4}H_{9}S&\rm \cdot &\rm +H\longrightarrow 1\hbox{-}C_{4}H_{9}SH\ast & (3)\cr } \bigskip\rm{}Relative rates of molecular elimination of hydrogen sulfide and C—S bond fission for the chemically activated 1-butanethiol, k5/k4 and k6/k4, were 0.114 and 0.0552 under 532 Pa of pressure at room temperature. Activation energies of the two reactions were calculated to be 228 [kJ/mol] and 297 [kJ/mol], respectively, by use of RRKM on the base of estimated A factors.\scriptfont4=\seveni \scriptscriptfont4=\fivei \halign{\hfill $#$&$#$\hfill &$#$\hfill &\hfill\qquad\qquad #\cr\rm 1\hbox{-}C_{4}H_{9}SH\ast +M&\rm \longrightarrow &\rm 1\hbox{-}C_{4}H_{9}SH& (4)\cr \rm 1\hbox{-}C_{4}H_{9}SH\ast &\rm \longrightarrow &\rm 1\hbox{-}C_{4}H_{8}+H_{2}S& (5)\cr\rm 1\hbox{-}C_{4}H_{9}SH\ast &\rm \longrightarrow &\rm 1\hbox{-}C_{4}H_{9}\cdot +HS\cdot & (6)\cr } \bigskip\rm{}© 1998 John Wiley & Sons, Inc. Int. J. Chem Kinet 30: 923-932, 1998
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  • 21
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    International Journal of Chemical Kinetics 30 (1998), S. 849-857 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aminolyses of the title substrates with anilines and benzylamines are investigated in acetonitrile. A clean second-order kinetics is obtained with a first-order rate law in the amine concentration, which is uncomplicated by the fast proton transfer step. The large magnitude of ρZ (ρ1g) as well as ρX (ρnuc) together with relatively large positive ρXZ values is consistent with a stepwise mechanism in which thiophenolate ion expulsion from the intermediate is rate limiting. For the reactions of aryl dithio-2-thiophenates with benzylamines the magnitude of ρX and ρZ values is relatively smaller suggesting that both the addition and expulsion of thiophenolate are partially rate determining. Relatively large secondary kinetic isotope effects, kH/kD≥1.7, with deuterated nucleophiles, support involvement a concurrent proton transfer to the departing thiophenolate ion in the transition state. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 849-857, 1998
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  • 22
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    International Journal of Chemical Kinetics 30 (1998), S. 899-902 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stoichiometry of CO2 production during the ceric oxidation of various organic acids is measured under conditions with organic acid excess. Measurements utilize a photometric methodology. For anaerobic conditions stoichiometries [CO2]produced:[Ce(IV)]reduced of about 0 (malonic acid), 0.5 (e.g., glyoxylic acid), and 1.0 (oxalic acid) are found. Oxalic acid showed an oxygen-induced decrease of CO2 production, while other compounds such as malonic acid increased the amount of produced CO2 or showed no changes (e.g., tartronic acid). In the case of mesoxalic acid the stoichiometry is increased from about 0.5 to 2.0 due to the presence of molecular oxygen. The results are discussed on the basis of simple reaction mechanisms demonstrating that useful information on reaction pathways and intermediates can be extracted from these simple measurements. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 899-902, 1998
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  • 23
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    International Journal of Chemical Kinetics 30 (1998), S. 7-19 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Manganese(III) solutions were prepared by known electrochemical methods in sulfuric acid, acetic acid, and pyrophosphate media. The nature of the oxidizing species present in manganese(III) solutions was characterized by spectrophotometric and redox potential measurements. Kinetics of oxidation of L-glutamine by manganese(III) in sulfuric acid (1.5 M), acetic acid (60% v/v), and pyrophosphate (pH=1.3) media at 313 K, 323 K, and 328 K, respectively, have been studied. Three different rate laws have been obtained for the three media. Effects of varying ionic strength, solvent composition, and added anions, such as fluoride, chloride, perchlorate, pyrophosphate, and bisulfate, have been investigated. There is evidence for the existence of free radicals as transient species. Activation parameters have been evaluated using Arrhenius and Eyring plots. Mechanisms consistent with the observed kinetic data have been proposed and discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 7-19, 1998.
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  • 24
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    International Journal of Chemical Kinetics 30 (1998), S. 63-67 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of reagent concentration and the pH in the kinetic behavior of the dissociation of Fe(II)-fulvic acid complexes were studied using a spectrophotometric technique. The results show that this behavior is not strongly affected by the concentration of fulvic acid, the concentration of the metal cation on the ratio of these concentrations and that variations in pH are more important in the dissociation process. A possible explanation based in the relative influence of proton concentration on the stability of the complexes is proposed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 63-67,1998.
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  • 25
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    International Journal of Chemical Kinetics 30 (1998), S. 111-120 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The detailed kinetics of the reaction of toluidine blue {phenothiazine-5-ium, 3-amino-7(dimethylamino)-2-methyl chloride, tolonium chloride, TB+Cl-} with potassium bromate and with aqueous bromine reaction were studied. In most of the experiments, the kinetics were monitored by following the rate of consumption of TB+ at 590 nm with excess acid and bromate. The reaction exhibited complex kinetic behavior. Initial reaction was slow and after an induction time, the TB+ concentration decreased fast. It had first-order dependence on both TB+ and bromate, and second-order dependence on H+. Under excess bromate conditions, the stoichiometric ratio of TB+ to bromate was 1:1. Demethylated sulfoxides were found at the reaction products. Sharp increase in the overall potential synchronized with the increase in bromine levels and the fast depletion of [TB+]. The role of bromide ion and bromine in the reaction was established. A multi-step reaction mechanism is proposed consistent with the experimental results. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 111-120, 1998.
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  • 26
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    International Journal of Chemical Kinetics 30 (1998), S. 145-150 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate constants were determined for the nitrosation reactions of the following substrates: Methyl (MU), Ethyl (EU),Propyl (PU)Butyl (BU), and Allylurea (AU). The rate equation found at a constant pH was: v=k[HNO2] [Urea]. The reactions were carried out in predominantly organic media(dioxane-acetic acid-water) with differing polarities. The proposed reaction mechanism involves the proton transfer from the protonated N-alkyl-N-nitrosourea to the acetate anion. As the polarity of the medium decreased, an approximation of the rate constants of the nitrosation of the different substrates was observed. This approximation can be interpreted as a function of the impediment generated by the R alkyl radical in the rate controlling step. Accordingly, the substrate reactivity will be associated with the ease in which the protonated N-alkyl-N nitrosurea can transfer the proton to the acetate anion. The results achieved in this study are in accordance with there activities observed in the nitrosation of these substrates in aqueous media MU≫(EU≈PU≈BU)〉AU. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 145-150, 1998.
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  • 27
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    International Journal of Chemical Kinetics 30 (1998), S. 185-191 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of decomposition of azetidine {(CH2)3N(SINGLEBOND)H)} was measured using single-pulse shock-tube techniques, over the temperature range 855-1100 K, in high argon dilution. These data confirm and extend an earlier investigation that utilized the very low-pressure pyrolysis method. A brief survey of many reports regarding the interesting features of azetidine is presented. In two appendices the thermodynamic and kinetic data on trimethylene sulfide, oxide, and immine are intercompared. New ab-initio calculations are cited for the parent species and their fragmentation products. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 185-191, 1998.
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  • 28
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    International Journal of Chemical Kinetics 30 (1998), S. 207-214 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Manganese(II) is oxidized by ozone in acid solution, k=(1.5±0.2)×103 M-1 s-1 in HClO4 and k=(1.8±0.2)×103M-1 s-1 in H2SO4. The plausible mechanism is an oxygen atom transfer from O3 to Mn2+ producing the manganyl ion MnO2+, which subsequently reacts rapidly with Mn2+ to form Mn(III). No free OH radicals are involved in the mechanism. The spectrum of Mn(III) was obtained in the wave length range 200-310 nm. The activation energy for the initial reaction is 39.5 kJ/mol. Manganese(III) is reduced by hydrogen peroxide to Mn(II) with k(Mn(III)+H2O2)=2.8×103M-1 s-1 at pH 0-2. The mechanism of the reaction involving formation of the manganese(II)-superoxide complex and reaction of H2O2 with Mn(IV) species formed due to reversible disproportionation of Mn(III), is suggested. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 207-214, 1998.
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  • 29
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    International Journal of Chemical Kinetics 30 (1998), S. 243-247 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nine amino acids, aspartic acid, glycine, serine, tyrosine, alanine, glutamic acid, threonine, cystine, phenylalanine, and two peptides, and two peptides, glycine-glycine peptide, glutamic acid-cystine-glycine peptide, give rise to damped oscillations of the Belousov-Zhabotinskii(BZ) type in a batch reactor. Both Mn2+ and Fe(phen)32 are essential for most of those oscillations; and the oscillations in [Mn3+] and [Fe(phen)33+] are also observed. The role of two metallic ions played in the oscillations are analyzed, showing that Mn2+ catalyzes the oxidation of the amino acids or peptides by BrO3- to produce some intermediates which effectively reduce Br2 to Br- catalyzed by Fe(phen)32+. © 1998 John Wiley & Sons, Inc. Int. J. Chem Kinet 30: 243-247, 1998.
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  • 30
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    International Journal of Chemical Kinetics 30 (1998), S. 267-272 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title reactions are subjected to a kinetic analysis in 44 wt% ethanol-water, at 25.0°C, ionic strength 0.2 (KCl). With a large excess of amine over the substrate, pseudo-first-order rate coefficients (kobs) are obtained, which are linearly dependent on the amine concentration. The nucleophilic rate constants (kN) are determined from plots of kobs vs. amine concentration. The Brönsted-type plot obtained with the kN values is linear, with slope β=0.63. The magnitude of this slope suggests that the mechanism is concerted, as opposed to a stepwise process with rate-determining breakdown of a zwitterionic tetrahedral intermediate (T±), in which the value of β is usually 0.8-1.0. The pyridinolysis of the same substrate in the same solvent is stepwise with the breakdown of T± as the rate-determining step. The change to a concerted mechanism for the title reactions is attributed to the superior nucleofugality of the alicyclic amines, compared to the isobasic pyridines, which destabilizes kinetically the “intermediate” T± in such a way that it does not exist, and the mechanism becomes enforced concerted. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 267-272, 1998.
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  • 31
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    International Journal of Chemical Kinetics 30 (1998), S. 309-310 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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  • 32
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    International Journal of Chemical Kinetics 30 (1998), S. 313-327 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By surveying the most used methods for evaluating the kinetic parameters from nonisothermal experiments, a new classification scheme of the methods is proposed. For each method the number of principles and theoretical approximations required to derive the equation which grounds it, is considered as a comparison criterion. The methods are, finally, classified into classes of equivalence.As a result of the analysis it is also suggested that the activation energy, as calculated from nonisothermal data, should be given as a range of values instead of a unique value. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 313-327, 1998.
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  • 33
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    International Journal of Chemical Kinetics 30 (1998), S. 329-333 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate coefficients for the reactions CHFO+F, CFO+F and the self-reaction of CFO were determined over the temperature range of 222-298 K. A computer controlled discharge-flow system with mass spectrometric detection was used. The results are expressed in the Arrhenius form (with energies in J):CHFO+F→CFO+HF:k1(T)=(9.7±0.7)·10-12 exp[-(5940±150)/RT] cm3 molecule-1 s-1CFO+F+M→CF2O+M:FORMULA DISC=“MATH”〉k2(T)=(2.60±1.17)·10-10 exp[-(10110±1250)/RT cm3 molecule-1 s-1FORMULACFO+CFO→CF2O+CO:k3(T)=(3.77±2.7)·10-10 exp[-(8350±2800)/RT] cm3 molecule-1 s-1© 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 329-333, 1998
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  • 34
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    International Journal of Chemical Kinetics 30 (1998), S. 359-366 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal dehydrochlorination CF2ClCH3→CF2(DOUBLEBOND)CH2+HCl has been studied in a static system between 597 and 664 K in the presence of CCl4, C2Cl6, CF2(DOUBLEBOND)CH2, HCl, and CF3CH3. A kinetic radical and molecular reaction model has been developed. In addition to describing earlier results on the acceleration of the pyrolysis by CCl4 and the further acceleration by HCl, this model describes quantitatively up to conversions of 20% (i) the dependence of the catalytic effect of CCl4 at low concentrations, (ii) the stronger catalytic effect of C2Cl6, and (iii) the inhibitory effect of added CF2CH2 and CF3CH3 when CCl4 is used as a catalyst. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 359-366, 1998
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  • 35
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    International Journal of Chemical Kinetics 30 (1998), S. 407-414 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the oxidation of aspirin (ASP) by bromamine-T (BAT), N-bromosuccinimide (NBS), and N-bromophthalimide (NBP) has been studied in aqueous perchloric acid at 303 K. The oxidation reaction follows identical kinetics with first-order in [oxidant], fractional-order in [ASP], and inverse fractional-order in [H+]. Under identical experimental conditions the extent of oxidation with different oxidizing agents is in the order: NBS 〉 BAT 〉 NBP. The rate decreased with decreasing dielectric constant of the medium. The variation of ionic strength and the addition of the reaction products and halide ions had no significant effect on the reaction rate. The solvent isotope effect was studied using D2O. Kinetic parameters were evaluated by studying the reaction at different temperatures. The reaction products were identified by GC-MS. The proposed reaction mechanism and the derived rate law are consistent with the observed kinetic data. Formation and decomposition constants for ASP-oxidant complexes have been evaluated. Decarboxylation, bromination, and loss of acetic acid gave 2,4,6-tribromophenol. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 407-414, 1998
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  • 36
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    International Journal of Chemical Kinetics 30 (1998), S. 425-437 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isobutane pyrolysis is studied in an unpacked Pyrex reactor at 20-100 torr initial pressures and 750-793 K. Results are interpreted in terms of a long chain radical mechanism and the reaction is modeled. The reaction selectivity or ratio of the initial production rate of isobutene (or hydrogen) to that of propene (or methane) is practically given by the ratio of the rate constant of abstraction of a tertiary hydrogen atom of isobutane to that of a primary one. A sensitivity analysis clearly shows that self-inhibition is essentially due to methylallyl radicals produced by hydrogen abstraction from isobutene. The model has been manually adjusted to experimental results and most of the adjusted rate constants are in agreement with literature data. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 425-437, 1998
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  • 37
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    International Journal of Chemical Kinetics 30 (1998), S. 463-469 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solvent effects on the kinetics of hydrolysis of isatin by sodium hydroxide have been investigated within the temperature range (30-55°C) in methanol-water and acetonitrile-water media of varying solvent compositions up to 70% (v/v) of the organic solvent component. The thermodynamic activation parameters were calculated and discussed in terms of solvation effects. The determined isokinetic temperatures, in both systems, revealed the existence of compensation effect arising from strong solute-solvent interactions; log k was correlated with both log [H2O] and the reciprocal of the dielectric constant. The first correlation was observed to be linear while the second was nonlinear. Finally a mechanism for the isatin ring opening was proposed, which accounts for the role and the effect of the solvent on the reaction rate. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 463-469, 1998
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  • 38
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    International Journal of Chemical Kinetics 30 (1998), S. 565-570 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tert-Butyl hydroperoxide and hydrogen peroxide readily react with the radical cation derived from 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). The reaction is inhibited by ABTS and protons, and can be interpreted in terms of a mechanism comprising a partially reversible electron transferROOH+ABTS•+↔ ROO · + ABTS + H+ (1)followed by the self-reactions of the hydroperoxide derived radicals and reactions between them and another ABTS derived radical. A complete kinetic analysis allows an evaluation of the rate constant for reaction (1). A value of 0.2 M-1 s-1 was obtained for both compounds. The back reaction of process (1) is more relevant when tert-butyl hydroperoxide is employed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 565-570, 1998
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  • 39
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    International Journal of Chemical Kinetics 30 (1998), S. 595-604 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a stirred batch reactor, the Ce(III)- or Mn(II)-catalyzed Belousov-Zhabotinsky reaction with mixed organic acid/ketone substrates exhibits oscillatory behavior. The organic acids studied here are: dl-mandelic acid (MDA), dl-4-bromomandelic acid (BMDA), and dl-4-hydroxymandelic acid (HMDA), and the ketones are: acetone (Me2CO), methyl ethyl ketone (MeCOEt), diethyl ketone (Et2CO), acetophenone (MeCOPh), and cyclohexanone ((CH2)5CO). The effects of bromate ion, organic acid, ketone, metal-ion catalyst, and sulfuric acid concentrations on the oscillatory patterns are investigated. Both conventional and stopped-flow methods are applied to study the kinetics of the oxidation reactions of the above organic acids by Ce(IV) or Mn(III) ion. The order of relative reactivities of the oxidation reactions of organic acids in 1 M H2SO4 is Mn(III)(SINGLEBOND)HMDA reaction 〉 Ce(IV)(SINGLEBOND)HMDA reaction 〉 Mn(III)(SINGLEBOND)BMDA, reaction 〉 Mn(III)(SINGLEBOND)MDA reaction 〉 Ce(IV)(SINGLEBOND)BMDA reaction 〉 Ce(IV)(SINGLEBOND)MDA reaction. Spectrophotometric study of the bromination reactions of the above ketones shows that these reactions are zero-order with respect to bromine and first-order with respect to ketone and that ketone enolization is the rate-determining step. The order of relative rates of bromination or enolization reactions of ketones in 1 M H2SO4 is (CH2)5CO≫(MeCOEt, Et2CO, Me2CO)〉MeCOPh. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet:30: 595-604, 1998
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  • 40
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    International Journal of Chemical Kinetics 30 (1998), S. 641-646 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of bromide ions to the component solutions of the Briggs- Rauscher oscillating system produces a variety of phenomena, depending on the sequence of the addition and on the initial bromide concentration. If the addition is made some minutes after the mixing of H2O2 and acidic IO3- and before adding malonic acid and Mn2+ ions, the oscillations last for five or six cycles, then suddenly ceases. If the addition is made immediately after the mixing of H2O2 and acidic IO3- and before adding malonic acid and Mn2+ ions, the oscillations do not start at all. The addition of bromide ions to an actively oscillating BR reaction causes a rapid suppression of the oscillations. Our observations may be accounted for by a mechanism involving the IBr species. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 641-646, 1998
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  • 41
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    International Journal of Chemical Kinetics 30 (1998), S. 683-697 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An experimental and theoretical study of the pyrolysis and oxidation of parabenzoquinone has been performed. The experiments were conducted in an isothermal quartz flow reactor at atmospheric pressure in the temperature range 600-1500 K. The main variables considered are temperature, oxygen concentration, and presence of CO. A detailed reaction mechanism for the pyrolysis and oxidation chemistry of parabenzoquinone is proposed, which provides a good description of the experimental results. Both the experimental work and the kinetic mechanism proposed for the pyrolysis and oxidation of parabenzoquinone represent the first systematic study carried out for this important aromatic compound.Our pyrolysis results confirm that the primary dissociation channel for p-benzoquinone leads to CO and a C5H4O isomer, presumably cyclopentadienone. However, significant formation of CO2 during the pyrolysis may indicate the existence of a secondary dissociation channel leading to CO2 and a C5H4 isomer. Under oxidizing conditions, consumption of p-benzoquinone occurs mainly by dissociation at lower temperatures. As the temperature increases interaction of OC6H4O with the radical pool becomes more significant, occurring primarily through hydrogen abstraction reactions followed by ring opening reactions of the OC6H3O radical. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 683-697, 1998
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  • 42
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    International Journal of Chemical Kinetics 30 (1998), S. 721-727 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate coefficients for the reactions of hydrogen atoms with n-C3H7Br, s-C3H7Br, n-C4H9Br, and s-C4H9Br were determined in a discharge flow-reactor at 298 K and a pressure of 4 mbar. Molecular-beam sampling and subsequent mass-spectrometric detection with electron-impact ionisation was used for the measurement of the bromo-hydrocarbon concentration. The rate coefficients obtained are (in 1010 cm3 mol-1 s-1): 2.3±1.2 for n-C3H7Br, 2.3±1.2 for s-C3H7Br, 2.4±1.2 for n-C4H9Br, and 2.8±1.4 for s-C4H9Br. The results are compared with predictions from bond-energy bond-order (BEBO) calculations, where a reasonable agreement is found. Furthermore, also by BEBO calculations, the relative importance of bromine abstraction as compared to hydrogen abstraction is estimated. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 721-727, 1998
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  • 43
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    International Journal of Chemical Kinetics 30 (1998), S. 769-776 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants for the reaction of ozone with methylvinyl ketone (H2C(DOUBLEBOND)CHC(O)CH3), methacrolein (H2C(DOUBLEBOND)C(CH3)CHO), methacrylic acid (H2C(DOUBLEBOND)C(CH3)C(O)OH), and acrylic acid (H2C(DOUBLEBOND)CHC(O)OH) were measured at room temperature (296±2 K) in the presence of a sufficient amount of cyclohexane to scavenge OH-radicals. Results from pseudo-first-order experiments in the presence of excess ozone were found not to be consistent with relative rate measurements. It appeared that the formation of the so-called Criegee-intermediates leads to an enhanced decrease in the concentration of the two organic acids investigated. It is shown that the presence of formic acid, which is known to react efficiently with Criegee-intermediates, diminishes the observed removal rate of the organic acids. The rate constant for the reaction of ozone with the unsaturated carbonyl compounds methylvinyl ketone and methacrolein was found not to be influenced by the addition of formic acid. Rate constants for the reaction of ozone determined in the presence of excess formic acid are (in cm3 molecule-1 s-1): methylvinyl ketone (5.4±0.6)×10-18; methacrolein (1.3±0.14)×10-18; methacrylic acid (4.1±0.4)×10-18; and acrylic acid (0.65±0.13)×10-18. Results are found to be consistent with the Criegee mechanism of the gas-phase ozonolysis. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 769-776, 1998
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  • 44
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An extension to the rotating-sector method, which is usually applied to determine propagation and termination rate constants, is presented. The analytical treatment developed accounts for the simultaneous presence of a thermal initiation and of a first-order termination process. The applicability of the rotating-sector method is thus extended to situations where the rate in dark is higher than 5% of the rate in the presence of light, and more accurate estimates of the rate constants are obtained than before for any values of the “dark” rate. A previously published experiment on the application of the rotating-sector method to the autoxidation of styrene was reanalyzed. The estimates obtained for the propagation and the termination rate constants were 11% and 19% higher than the previous estimates, respectively. Finally, the improved rotating-sector method was also applied to the experimental determination of propagation (kp) and termination rate constants (2×kt) for both 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine (PLPC) and 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLPC) liposomes. The following results were obtained at 37°C: for PLPC kp =16.6 M-1s-1, and 2×kt=1.27×105 M-1s-1; for DLPC kp(intermolecular)=(13.3-13.9) M-1s-1, kp(intramolecular)=(4.7-5.4) s-1, and 2×kt=(0.99-1.05)×105 M-1s-1. The separation of the intermolecular and intramolecular propagation rate constants for DLPC was made possible both by a special adaptation of the rotating-sector equations to substrates with two oxidizable moieties, and by the experimental determination of the ratio between partially oxidized DLPC molecules (only one acyl is oxidized) and fully oxidized DLPC molecules (both acyls are oxidized). © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 753-767, 1998
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  • 45
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    International Journal of Chemical Kinetics 30 (1998), S. 805-830 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A comprehensive detailed chemical kinetic mechanism for methanol oxidation has been developed and validated against multiple experimental data sets. The data are from static-reactor, flow-reactor, shock-tube, and laminar-flame experiments, and cover conditions of temperature from 633-2050 K, pressure from 0.26-20 atm, and equivalence ratio from 0.05-2.6. Methanol oxidation is found to be highly sensitive to the kinetics of the hydroperoxyl radical through a chain-branching reaction sequence involving hydrogen peroxide at low temperatures, and a chain-terminating path at high temperatures. The sensitivity persists at unusually high temperatures due to the fast reaction of CH2OH+O2=CH2O+HO2 compared to CH2OH+M=CH2O+H+M. The branching ratio of CH3OH+OH=CH2OH/CH3O+H2O was found to be a more important parameter under the higher temperature conditions, due to the rate-controlling nature of the branching reaction of the H-atom formed through CH3O thermal decomposition. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 805-830, 1998
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  • 46
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    International Journal of Chemical Kinetics 30 (1998), S. 869-874 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the reaction between BrO3- and sulfite was studied by measuring the concentrations of [Br-] and [H+] both in buffered and in unbuffered solutions. A mechanism was applied for simulation of the experimental observations. Rate constants k1=(0.027±0.004) M-1s-1 and k2=(85±5) M-1s-1 were determined for the following reactions:\halign{\hfill $#$\hfill &\hfill\qquad\qquad #\cr 3\ \rm HSO_{3}\!^{-}+BrO_{3}\!^{-}\longrightarrow 3\ SO_{4}\!^{2-}+Br^{-}+3\ H^{+}& (1)\cr 3\ \rm H_{2}SO_{3}(\hbox{or}\ SO_{2.}\hbox{aq})+BrO_{3}\!^{-}\longrightarrow 3\ SO_{4}\!^{2-}+Br^{-}+6\ H^{+}& (2)\cr }Rate constant k1 was obtained directly from the experimental results on unbuffered reactions, where Reaction (1) was predominant. Rate constant k2 was obtained by computer fitting of [Br-] to the experimental values for buffered reactions, where the rate of Reaction (2) was about four times higher than that of Reaction (1). © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 869-874, 1998
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  • 47
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    International Journal of Chemical Kinetics 30 (1998), S. 859-867 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Br-atom atomic resonance absorption spectrometry (ARAS) has been developed and applied to measure thermal decomposition rate constants for CF3Br (+ Kr)→CF3+Br (+ Kr) over the temperature range, 1222-1624 K. The Br-atom curve-of-growth (145〈λ〈163 nm) was determined using this reaction. For [Br]≤1×1012 molecules cm-3, absorbance, (ABS)=1.410×10-13 [Br], yielding σ=1.419×10-14 cm2. The curve-of-growth was then used to convert (ABS) to Br-atom profiles which were then analyzed to give measured rate constants. These can be expressed in second-order by k1=8.147×10-9 exp(-24488 K/T) cm3 molecule-1 s-1 (±33%, 1222≤T≤1624 K). A unimolecular theoretical approach was used to rationalize the data. Theory indicates that the dissociation rates are closer to second- than to first-order, i.e., the magnitudes are 30-53% of the low-pressure-limit rate constants over 1222-1624 K and 123-757 torr. With the known, E0=ΔH00=70.1 kcal mole-1, the optimized theoretical fit to the ARAS data requires 〈ΔE〉down=550 cm-1. These conclusions are consistent with recently published data and theory from Kiefer and Sathyanarayana. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 859-867, 1998
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  • 48
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 49
    ISSN: 0268-2605
    Keywords: Nickel-σ-organyl complexes ; dispersed atomic Ni(0) ; Ni(I) ions ; silica ; EPR ; FMR ; spectrum calculation ; strain ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dispersed atomic nickel(0) is formed during the reaction of the nickel-σ-organyl complexes with silanol groups at temperatures below 373 K. That nickel is oxidized to Ni(I) by protons of the silanol groups in a consecutive step. The Ni(I) portion amounts to about 70% w/w of the Ni used. Six different Ni(I) species are detected by electron paramagnetic resonance. They are stabilized by interaction with the silica surface and the organic moieties; they act as anchor ions for the Ni(0) atoms. Ni(0) crystallites stabilized in this way are about 0.5 nm in diameter after a treatment at 373 K. The influence of the Ni(I) ions on the collective, magnetic properties of the clusters is revealed by calculation of ferromagnetic resonance (FMR) spectra using the independent-grain approach according to Schlömann and Kotyukov. A strain of about 10 GPa is brought about in the nickel crystallites by the interaction with Ni(I) ions. © 1998 John Wiley & Sons, Ltd.
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  • 50
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    Applied Organometallic Chemistry 12 (1998), S. 375-379 
    ISSN: 0268-2605
    Keywords: granular films ; pulsed laser deposition ; giant magnetoresistance ; microstructure ; magnetic properties ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An investigation into the microstructural properties of CoxAg1 - x films, grown by pulsed laser deposition, as a function of deposition and post-deposition annealing temperature is reported. Surface morphology and microstructure were investigated by XPS, SEM and TEM measurements. Magnetic measurements were used to gain further information on particle size distributions through the analysis of the temperature dependence of the irreversible magnetization. Depending on cobalt content, deposition and post-deposition annealing temperature, the maximum of the cobalt grains diameter distribution was estimated to be in the range 2-6 nm. © 1998 John Wiley & Sons, Ltd.
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  • 51
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    Applied Organometallic Chemistry 12 (1998), S. 381-386 
    ISSN: 0268-2605
    Keywords: nanoparticles ; magnetic susceptibility ; magnetic anisotropy ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dynamical behavior of γ-Fe2O3 particles dispersed in a polymer have been investigated by a.c. susceptibility and Mössbauer spectroscopy measurements. The effect of interparticle interactions on the relaxation time is satisfactorily described by a superparamagnetic model where the dipolar energy is determined by a statistical calculation for a disordered arrangement of particles with volume distribution and easy axes in random orientations. The results indicate that the single particle anisotropy energy is mainly determined by surface anisotropy and that the energy barrier increases with the interaction strength. © 1998 John Wiley & Sons, Ltd.
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  • 52
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    Applied Organometallic Chemistry 12 (1998), S. 467-467 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 53
    ISSN: 0268-2605
    Keywords: fungicidal activity ; Ceratocystis ulmi ; triphenyltin(IV) ; tributyltin(IV) ; phenolic bridge ; carboxylate bridge ; polymers ; trigonal bipyramidal structures ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The methods of synthesis, elemental analysis, IR and NMR spectroscopic data and fungicidal activity against Ceratocystis ulmi are reported for a series of triorganotin esters of N-arylidene-ω-amino acids of general formula R3SnOCO(CH2)nN = CHAr (R = Ph, n-Bu; Ar = 2-HOC6H4, 2-HOC10H6; n = 1, 2, 3 and 5). The crystal structures for two of the compounds, tributyltin N-2-hydroxynaphthalidene glycinate (1) and tributyltin N-2-hydroxynaphthalidene-β-alaninate (2), have been determined. Although both of these compounds have a trans-R3SnO2 structure, in compound 1 the carboxylate group is monodentate and the fifth coordination position around the tin atom is taken up by a coordinated phenolic group, whereas in 2 the carboxylate group is bridging. These two examples thus correspond to the two different structures reported for trans-R3SnO2 complexes. Both compounds were found to be active against Ceratocystis ulmi, but there was no significant difference in their levels of biological activity against this particular fungus. Apart from compound 1, the other tributyltin compounds reported are believed to adopt the carboxylate bridging mode shown by compound (2).Crystal data: for 1, crystals monoclinic, space group P21/c, a = 12.9435(11) Å, b = 13.5769(10) Å, c = 15.7715(12) Å, β = 108.919(6)°, Z = 4, Rf = 0.046 and Rw = 0.058 for 1448 significant reflections; for 2, crystals monoclinic, space group C 2/c,a = 24.588(14) Å, b = 9.733(3) Å, c = 27.611(12) Å,β = 113.49(4)°, Z = 8, Rf = 0.053 and Rw = 0.069 for 3822 significant reflections. © 1998 John Wiley & Sons, Ltd.
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  • 54
    ISSN: 0268-2605
    Keywords: density functional calculation ; binuclear metal carbonyl ; Cr2(CO)6+ ; laser ablation ; molecular beam ; optimized structures ; dissociation energy ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Density functional calculations have been made on a binuclear metal carbonyl ion Cr2(CO)6+ found in our laser ablation-molecular beam (LAMB) experiment. Optimized structures are calculated for three different conformations: T33 of D3d symmetry with three terminal carbonyl groups on each chromium atom, B2T22 of D2h symmetry with two bridging carbonyl groups and two terminal carbonyl groups on each chromium atom, and B4T11 of D4h symmetry with four bridging carbonyl groups and one terminal carbonyl group on each chromium atom. The most stable conformation is T33 which is 36.76 and 286.44 kJ mol-1 lower in energy than B2T22 and B4T11, respectively. The difference of conformation exerts a significant influence on the internuclear distance between chromium and the carbon of terminal CO, but hardly on the Cr-Cr bond length. For B2T22 and B4T11, longer C-O distances for bridging carbonyls compared with those for terminal ones indicate effective π*-back donation from the chromium atom to the bridging carbonyl groups. Furthermore, the relative abundance of Cr2(CO)n+ (n = 0-6) observed in our previous experimental study can be explained qualitatively by comparison of the excess energy produced in the formation of a Cr+-Cr bond with the CO dissociation energy of Cr2(CO)6+. © 1998 John Wiley & Sons, Ltd.
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  • 55
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    Applied Organometallic Chemistry 12 (1998), S. 467-468 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 56
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    Applied Organometallic Chemistry 12 (1998), S. 468-468 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 57
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 58
    ISSN: 0268-2605
    Keywords: metal clusters ; quantum-size effect ; nanostructures ; size effects ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Meta-cluster compounds can be exploited advantageously to study the evolution, with increasing size of the molecules of the physical properties of metal clusters from molecular to bulk-metal behavior. The metal-cluster molecules are well-defined, stoichiometric, chemical compounds. The molecules consist of a metal core of a variable number of atoms, surrounded by a shell of ligand atoms or molecules. Depending on the compound, the type of metal atom may be varied, whereas the core size can be changed from a few up to several thousands of atoms. Accordingly, these materials provide excellent model systems for monodisperse metal particles, embedded in a dielectric matrix, and can be investigated by the well-known experimental techniques of solid-state physics. © 1998 John Wiley & Sons, Ltd.
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  • 59
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    Applied Organometallic Chemistry 12 (1998), S. 475-478 
    ISSN: 0268-2605
    Keywords: organomercurials ; symmetrization ; column chromatography ; organomercury halides ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The symmetrization reaction of organomercury(II) chlorides (RHgCl) to R2Hg and HgCl2 in toluene solution under identical conditions using a basic alumina column has been studied­in order to compare the effect of the nature of the R groups on the extent of symmetrization. The efficiency of symmetrization depends markedly on the electron-withdrawing nature of­R, varying from 90-94% for R = trichlorovinyl or phenyl to 11% for R = 2,6-dimethylphenyl.© 1998 John Wiley & Sons, Ltd.
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  • 60
    ISSN: 0268-2605
    Keywords: HPLC-ICP-MS ; cetaceans ; pinnipeds ; arsenic ; arsenobetaine ; arsenocholine ; whales ; seals ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Total arsenic concentrations and the concentrations of individual arsenic compounds were determined in liver samples of pinnipeds [nine ringed seals (Phoca hispida), one bearded seal (Erginathus barbatus)] and cetaceans [two pilot whales (Globicephalus melas), one beluga whale (Deliphinapterus leucus)]. Total arsenic concentrations ranged from 0.167 to 2.40 mg As kg-1 wet mass. The arsenic compounds extracted from the liver samples with a methanol/water mixture (9:1, v/v) were identified and quantified by anion- and cation-exchange chromatography. An ICP-MS equipped with a hydraulic high-pressure nebulizer served as the arsenic-specific detector. Arsenobetaine (0.052-1.67 mg As kg-1 wet mass) was the predominant arsenic compound in all the liver samples. Arsenocholine was present in all livers (0.005-0.044 mg As kg-1 wet mass). The tetramethylarsonium cation was detected in all pinnipeds (〈0.009 to 0.043 mg As kg-1) but not in any of the cetaceans. The concentration of dimethylarsinic acid ranged from 〈 0.001 to 0.109 mg As kg-1 wet mass. Most of the concentrations for methylarsonic acid (〈0.001 to 0.025 mg As kg-1 wet mass) were below the detection limit. Arsenous acid and arsenic acid concentrations were below the detection limit of the method (0.001 mg As kg-1). An unknown arsenic compound was present in all liver samples at concentrations from 0.002-0.027 mg As kg-1. © 1998 John Wiley & Sons, Ltd.
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  • 61
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    Applied Organometallic Chemistry 12 (1998), S. 520-520 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 62
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    Applied Organometallic Chemistry 12 (1998), S. 520-520 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 63
    ISSN: 0268-2605
    Keywords: organotin ; N-(2-pyridylmethylene)arylamines ; IR ; NMR ; Mössbauer ; mutagenicity ; sister chromatid exchange ; cell cycle delay ; bone-marrow cells ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diorganotin(IV) dichloride complexes of the type R2SnCl2·L (R = methyl, ethyl, vinyl, t-butyl, n-butyl or phenyl; L = N-(2-pyridylmethylene)arylamine) have been synthesized and characterized on the basis of IR, NMR and 119Sn Mössbauer studies. Investigation of the complexes indicated that N-(2-pyridylmethylene)arylamines form distorted trans-octahedral complexes with R2SnCl2 similar to the well-known R2SnCl2·L. Cytogenetic toxicology testing has been performed for Et2SnCl2·L4 [L4 = N-(2-pyridylmethylene)-4-toluidine] in mouse bone-marrow cells in vivo since such testing is a regulatory requirement before new drugs are released. This tin compound induced delay in cell-cycle kinetics and sister chromatid exchanges (SCEs) significantly. The effect of Et2SnCl2·L4 was greater when endogenous glutathione (GSH) was depleted by buthionine sulphoximine (BSO). It seems that Et2SnCl2·L4 induces SCEs due to formation of adduct by binding on DNA which could interfere in DNA synthesis and cause delay in cell proliferation. Depletion of GSH could reduce the shielding effect of GSH on chromatin and allows more Et2SnCl2·L4 to bind on DNA. © 1998 John Wiley & Sons, Ltd.
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  • 64
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
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  • 65
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    Applied Organometallic Chemistry 12 (1998), S. 878-878 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
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  • 66
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    Applied Organometallic Chemistry 12 (1998), S. 884-884 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
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  • 67
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    Applied Organometallic Chemistry 12 (1998), S. 883-884 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
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  • 68
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 69
    ISSN: 0268-2605
    Keywords: methylmercury ; analysis ; HPLC- ICP MS ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel technique has been developed for the determination of trace amounts of methylmercury in various sample matrices. The newly developed HPLC method makes it possible to separate methylmercury and inorganic mercury with ultrasonic nebulization and detection by ICP MS for different mercury isotopic masses. The isotope-specific detection allows the application of the species-specific isotope addition method for the determination of methylmercury with a correction for artifact formation. The well-known water-vapour distillation method was used in combination with an enriched stable inorganic mercury isotope (200Hg2+) for the separation of methylmercury from various matrices. The subsequent determination of CH3 - 200Hg+ generated from 200Hg2+ was used in the correction for artifact formation during sample preparation. In comparison with a previously developed HPLC coupling technique with HPF-HHPN (high-performance flow/­hydraulic high-pressure nebulization), the stability of the detection procedure was improved considerably. The limit of detection (S/N = 3) for methylmercury was calculated to be about 0.015 μg kg-1. © 1998 John Wiley & Sons, Ltd.
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  • 70
    ISSN: 0268-2605
    Keywords: methylmercury ; solid-phase microextraction ; gas chromatography-atomic fluorescence ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analytical method is described for methylmercury determination in fish and aqueous samples using solid-phase microextraction (SPME) followed by gas chromatography-atomic fluorescence spectrometry (GC-AFS). The procedure involves aqueous-phase derivatization of methylmercury species with sodium tetraethylborate in a sample vial and subsequent extraction with a silica fiber coated with poly-­(dimethylsiloxane). The mercury derivatives are desorbed in the splitless injection port of a gas chromatograph and subsequently analyzed by GC-AFS. The headspace SPME procedure is used and parameters affecting the extraction, adsorption and desorption are evaluated. Results for methylmercury analysis in standard reference material (DORM-2) and fish samples are presented. © 1998 John Wiley & Sons, Ltd.
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  • 71
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    Applied Organometallic Chemistry 12 (1998), S. 571-576 
    ISSN: 0268-2605
    Keywords: zerovalent metals ; bromoalkyltriphenylphosphonium bromides ; methylmercuric acetate ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aqueous solutions of bromoalkyltriphenylphosphonium bromides react with zerovalent metals, causing their dissolution. The reaction initially follows second-order kinetics, with the rate depending on both metal and bromide concentrations. Zerovalent metals similarly react with aqueous methylmercuric acetate and other dissolved organometals. © 1998 John Wiley & Sons, Ltd.
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  • 72
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    Applied Organometallic Chemistry 12 (1998), S. 659-666 
    ISSN: 0268-2605
    Keywords: polymers ; polyphosphazenes ; synthesis ; surfaces ; surface reactions ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The macromolecular substitution approach for the synthesis of polyphosphazenes provides access to many different polymers. However, it precludes the use of reagents that contain two or more functional groups because such compounds would cause extensive crosslinking of the chains. This presents a problem because many of the uses for which polyphosphazenes seem ideally suited require the presence of -OH, -COOH, -NH2, -SO3H, -PR2 and other functional units in the side-chain structure. We have developed two approaches to introduce such active sites: (1) protection-deprotection reactions; and (2) direct reactions of active reagents with the organic side-groups of non-functional poly(organophosphazenes). These methods have been applied both at the molecular level and in the form of reactions carried out only at polymer surfaces. The resultant polymers have special properties that are valuable in the micro-encapsulation of sensitive biological agents; in the formation of hydrophobic, hydrophilic, or adhesive surfaces; in crosslinking reactions; and in the development of solid polymer electrolytes, bio-erodible polymers, pH-triggered hydrogels, polymer blends and interpenetrating polymer networks. Overall, more than 700 different polyphosphazenes are now known, and a large number of these are functional macromolecules targeted for specific property combinations and uses. © 1998 John Wiley & Sons, Ltd.
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  • 73
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    Applied Organometallic Chemistry 12 (1998), S. 707-713 
    ISSN: 0268-2605
    Keywords: polyhedral oligomeric silsesquioxane ; hybrid ; thermoplastic ; polymer ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A diverse and entirely new class of monomer and polymer technology based on polyhedral oligomeric silsesquioxane (POSS) reagents has been developed. POSS reagents are unique in that they are physically large (approx. 15 Å diameter and 1000 amu) and are composed of a robust silicon-oxygen framework that can be easily functionalized with a variety of organic substituents. Appropriate functionalization of POSS cages allows for their incorporation into traditional thermoplastic resins without modification of existing manufacturing processes. The incorporation of POSS segments into linear copolymer systems results in increased glass transition and decomposition temperatures, increased oxygen permeability and reduced flammability and heat evolution, as well as modified mechanical properties relative to conventional organic systems. © 1998 John Wiley & Sons, Ltd.
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  • 74
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    Applied Organometallic Chemistry 12 (1998), S. 667-673 
    ISSN: 0268-2605
    Keywords: polysilanes ; poly(dimethylsiloxane) ; polyphosphazenes ; atom transfer radical polymerization ; controlled/‘living’ radical polymerization ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recent advances in the synthesis of block, graft and star polymers containing inorganic macromolecular species are described. Anionic copolymerization techniques were used in the for-­mation of diblock copolymers of poly(styrene-block-methylphenylsilylene) and poly(isoprene-block-methylphenylsilylene) by the ring-opening polymerization of 1,2,3,4-tetramethyl-1,2,3,4-tetraphenylcyclotetrasilane initiated by living anionic polystyrene and isoprene respectively. Hydrosilation of an attachable initiator onto telechelic vinyl- or hydrosilyl-terminal or­-pendant poly(dimethylsiloxane) (PDMS) yielded a PDMS macroinitiator. This macroinitiator was used in atom transfer radical polymerization (ATRP) of styrene and isobornyl acrylate to produce ABA triblock copolymers. As a model for graft copolymers from a polyphosphazene backbone, chemical trans-­formation of hexachlorocyclotriphosphazene­resulted in hexafunctional molecules containing either benzyl bromide or bromopropionyl moieties. The initiator 1,1,3,3,5,5-hexakis[4-(2-bromopropionyloxymethyl)phenoxy]cyclotriphosphazene was used in the ATRP of styrene to yield a polymer with a narrow, monomodal molecular weight distribution. Chain extension of this star polymer with isobornyl acrylate is also described. © 1998 John Wiley & Sons, Ltd.
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  • 75
    ISSN: 0268-2605
    Keywords: polymer ; organocobalt ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rearrangement reaction of an organocobalt polymer with cobaltacyclopentadiene moieties in the main chain (1) was carried out to yield a­new polymer bearing (η5-cyclopentadienyl) (η4-­cyclobutadiene)cobalt moieties in the main chain (2). For instance, a polymer (2) containing pure η4-cyclobutadienecobalt units was obtained as a yellow powder in 79% yield by the reaction of 1 in tetrahydrofuran (THF) at 110 °C for 1 h in a sealed tube. The polymer (2) obtained was soluble in organic solvents such as chloroform, THF and N,N-dimethylformamide and was quite stable under air. It showed good thermal stability and a weight loss of 5% was observed at 482 °C by thermogravimetric analysis (TGA). On the other hand, displacement of the triphenylphosphine ligands on the main chain of the organocobalt polymer (1), without rearrangement of the cobaltacyclopentadiene rings, was observed when the reaction was carried out in the presence of appropriate ligands such as P(n-Bu)3. The resulting ligand-exchanged polymer showed different properties in comparison with 1. For instance a polymer bearing tri-n-octylphosphine is soluble in n-hexane, which is a poor solvent for 1. © 1998 John Wiley & Sons, Ltd.
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  • 76
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    Applied Organometallic Chemistry 12 (1998), S. 749-753 
    ISSN: 0268-2605
    Keywords: polymer ; silicon ; gel ; films ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of organic-inorganic polymer hybrids consisting of carbon-carbon and siloxane chains was investigated by radical polymerization of 3-methacryloxypropyltrimethoxysilane (MAS) followed by acid-catalyzed hydrolytic polycondensation. The condensation of poly(3-methacryloxypropyltrimethoxysilane) (S-PMA) of various molecular weights Mn =830-12000 prepared by polyaddition provided transparent and flexible free-standing hybrid gel films. The mechanical properties of these films were highly dependent on the carbon-carbon chain length: with an increase in the carbon-carbon chain length, the elasticity of gel films increased, while the tensile strength and Young's modulus decreased. Hydrolyzability of S-PMA decreased with an increase in the carbon-carbon chain length, resulting in the formation of rubber-like films with flexibility. © 1998 John Wiley & Sons, Ltd.
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  • 77
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    Applied Organometallic Chemistry 12 (1998), S. 755-762 
    ISSN: 0268-2605
    Keywords: poly(vinyl alcohol) (PVA) ; sol-gel ; polymer hybrid ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Homogeneous poly(vinyl alcohol) (PVA)-silica gel polymer hybrids were prepared by in-situ hydrolysis of poly(vinyl acetate) (PVAc) in a sol-gel reaction mixture with tetramethoxysilane (TMOS). The degree of hydrolysis was evaluated by FTIR and 13C CP/MAS NMR; it increased with an increase in the acid catalyst and reached 85% with 1.6 ml of 0.1 M HCl. The homogeneity of the polymer hybrids obtained was maintained when the reaction was performed at 60 °C. However, the polymer hybrid became turbid with an increase of the amount of catalyst present when the reaction was conducted at room temperature. The homogeneity of the polymer hybrids obtained was evaluated by nitrogen sorption porosimetry of a porous silica that was obtained by charring the PVA hybrid. The results confirmed the molecular-level dispersion of the PVA in the hybrid. © 1998 John Wiley & Sons, Ltd.
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  • 78
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    Applied Organometallic Chemistry 12 (1998), S. 781-785 
    ISSN: 0268-2605
    Keywords: phosphonium ; polymer ; monomer ; film ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(arylene ether) main-chain phosphonium ionomers were successfully synthesized and characterized. The reaction scheme involved first preparing the poly(arylene ether phosphine oxide) by a nucleophilic step or condensation polymerization of bisphenolates on activated aryl halides, wherein phenyl phosphine oxide was the activating group. High-molecular-weight, tough, film-forming polymers were produced with glass transition temperatures of 200°C or higher. The resulting materials were successfully reduced using phenylsilane in refluxing chlorobenzene. The derived phosphine or phosphine/phosphine oxide copolymer was reacted with alkyl halides to produce the phosphonium salts. The resulting materials showed enhanced hydrophilicity and in some cases could be successfully dispersed in water. In addition, chromophores such as Methyl Orange and Methyl Red were combined with the backbone ionomer to produce new film-forming, ionically linked species. The materials are of general interest for situations where water-dispersible intermediates, e.g. coatings, fiber sizings etc. are required. The phosphonium salts can be converted back to the phosphine oxide in fairly high yields by simple thermal methods and in quantitative yield by chemical methods (e.g. the Wittig reaction). © 1998 John Wiley & Sons, Ltd.
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  • 79
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    Applied Organometallic Chemistry 12 (1998), S. 681-693 
    ISSN: 0268-2605
    Keywords: ceramics ; preceramic polymers ; SiNCB composites ; boron nitride ; boron ; silicon ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Our recent work directed at the design, synthesis, characterization and applications of new types of polyborazylene and polyborosilazane polymers is reviewed with a focus on the use of these polymers as processable precursors to BN and SiNCB composites. A design strategy based on the controlled functionalization of preformed polymers with pendant groups of suitable compositions and crosslinking properties has been employed to yield second-generation dipentylamine-polyborazylene (DPA) and pinacolborane-hydridopolysilazane (PIN-HPZ) polymers, which, unlike the parent polyborazylene (PB) and the borazine-hydridopolysilazane (B-HPZ) polymers, are stable as melts and can be easily melt-spun into polymer fibers. Subsequent pyrolyses of these polymer fibers then provide excellent routes to BN and SiNCB ceramic fibers. © 1998 John Wiley & Sons, Ltd.
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  • 80
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    Applied Organometallic Chemistry 12 (1998), S. 1-12 
    ISSN: 0268-2605
    Keywords: reaction ; morin ; hydroxyflavone ; preconcentration ; sample clean-up ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analytical procedure for the determination of phenyltin compounds in environmental sample waters was studied. Chromatography of mono-, di- tri-phenyltin (MPT, DPT and TPT) was performed on a reversed-phase C18 column with the mobile phase comprising methanol/10-2 M H3PO4 (80:20 v/v) at pH 3 and UV detection at 214 nm. To enhance the sensitivity of the detection system, the post-column reaction between morin or 3-hydroxyflavone and phenyltin compounds was formed before fluorescence detection. Several parameters affecting the fluorescence intensity were studied systematically, including the optimum condition for the post-column reagent that was also compatible with the eluent. The parameters concerned in this study were the pH, the percentage of Triton X-100, the ratio of fluorigenic reagent to phenyltin compounds and the amount of methanol in the eluent. Detection limits before the preconcentration process were in the region of 1.5 ppb for TPT and 150-250 ppb for MPT and DPT, respectively. Utilizing solid-phase extraction on a C18 cartridge for sample clean-up as well as preconcentration successfully reduced the detection limit of TPT to the level of ng dm-3 and can be applied to seawater analysis. Recovery in the range 95.0-98.0% was obtained by developing the optimum elution profile in the preconcentration step. © 1998 John Wiley & Sons, Ltd.
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  • 81
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 82
    ISSN: 0268-2605
    Keywords: X ray structure ; triphenyltin ; p-ethoxybenzoic acid ; acetylsalicylic acid ; phthalic acid ; salicylaldehydato ; polymer ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Triphenyltin(IV) compounds of p-ethoxybenzoic acid and acetylsalicylic acid contain molecular units with Sn-O bonds and distorted tetrahedral tin centers. The phthalic acid derivative contains two four-coordinate tin atoms between which the phthalic acid unit effectively forms a bridge. The salicylaldehydato compound is polymeric with trigonal bipyramidal tin centers in which the phenyl groups take equatorial positions. The polymerization occurs via the aldehyde oxygen atom bonding to a neighboring tin atom. © 1998 John Wiley & Sons, Ltd.
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  • 83
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    Applied Organometallic Chemistry 12 (1998), S. 25-30 
    ISSN: 0268-2605
    Keywords: adduct ; carboxylate ; Ceratocystis ulmi ; Dutch elm disease ; far-infrared spectroscopy ; fungicide ; Mossbauer spectroscopy ; organotins ; QSAR ; thiazolidin-4-ones ; triphenyltin ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the interest of developing a more effective fungicide to combat Dutch elm disease, our laboratories have synthesized several triphenyltin carboxylates and some 1:1 addition compounds of triphenyltin chloride using 2,3-disubstituted thiazolidin-4-ones as the ligand and screened them in vitro against Ceratocystis ulmi, the causative agent of Dutch elm disease, using a shake culture method. Elemental analyses and spectroscopic data indicate that the structures of the carboxy- lates in the solid state are monomeric with a tetrahedral tin atom with the exception of the furan-2-carboxylic acid derivative, which was found to be polymeric. The triphenyltin chloride adducts are trigonal-bipyramidal with the three phenyl groups in the equatorial plane. Far-infrared data indicate that the three phenyl groups are not co-planar. Screening results for both series of organotins indicate that these two classes of compounds are effective inhibitors of Ceratocystis ulmi, with the adducts having a higher activity. The furan-2-carboxylic acid derivative has a markedly decreased activity compared with the other carboxylates and this is attributed to its polymeric structure. © 1998 John Wiley & Sons, Ltd.
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  • 84
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    Applied Organometallic Chemistry 12 (1998), S. 78-78 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 85
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    Applied Organometallic Chemistry 12 (1998), S. 39-46 
    ISSN: 0268-2605
    Keywords: organotin(IV): organosilicon(IV) complexes ; thiosemicarbazones ; antimicrobial studies ; NMR spectra ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diorganotin(IV) and diorganosilicon(IV) derivatives of the types R2MCl(TSCZ) and R2M(TSCZ)2 (where TSCZ is the anion of a thiosemicarbazone ligand, R=Ph or Me and M=Sn or Si) have been synthesized and characterized by elemental analyses, molecular weight determinations and conductivity measurements. The mode of bonding has been established on the basis of IR and 1H, 13C 29Si and 119Sn NMR spectroscopic studies. Some of the representative complexes have also been evaluated for their antimicrobial effects on different species of pathogenic fungi and bacteria in vivoas well as in vitro.The results of these investigations are reported. © 1998 John Wiley & Sons, Ltd.
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  • 86
    ISSN: 0268-2605
    Keywords: triarylantimony dichrysanthemate ; plant growth-regulating activity ; crystal structure ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of triarylantimony dichrysanthemate compounds of the type Ar3Sb(O2CR)2 [Ar=C6H5, 4-CH3C6H4, 3-CH3C6H4, -CH3C6H4, 4-ClC6H4; R=4-ClC6H4CH(i-Pr), cis-Cl2C:CH trans-Cl2C:CH] have been synthesized and characterized by elemental analysis, infrared spectra, 1H NMR spectra and mass spectra. Some activities of these compounds in plant growth regulation have been determined. Their results indicate that the derivatives of cis-dichlorochrysanthemic acid and trans-dichlorochrysanthemic acid significantly promote rooting of excised cucumber cotyledons at 10 ppm. An X ray structure determination has been carried out as follows for Ph3Sb(O2CCHCMe2CMe2)2: orthorhombic, space group Pbcn, Z=4, structure solution with 2385 independent reflections, R=0.035. Lattice dimensions at 26 °C: a=15.616(3) Å, b=10.275(2) Å, c=20.201(5) Å, V=3241(2) Å3, ρ=1.302 g cm-3. © 1998 John Wiley & Sons, Ltd.
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  • 87
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    Applied Organometallic Chemistry 12 (1998), S. 59-65 
    ISSN: 0268-2605
    Keywords: cobaltocenium ; ferrocene ; Nafion ; phenytoin ; phenobarbital ; square-wave voltammetry ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two different cationic redox labels, i.e. a ferroceneammonium ion and a cobaltocenium ion, were covalently attached to two antiepileptics, phenytoin and phenobarbital, respectively. The two labeled drugs possess distinct standard redox potentials of 0.39 V for the phenytoin derivative and -0.92 V for phenobarbital derivative (vs Ag/AgCl, Cl- 0.05 M) at a carbon paste electrode. After preconcentration in a polyanionic Nafion-loaded carbon paste electrode the positively charged labeled phenytoin and phenobarbital derivatives could be simultaneously detected in concentration ranges which were relevant to the therapeutic ranges of the antiepileptics, with a view to a future dual-analyte immuno- assay. Square-wave voltammetry permitted detection limits of 5×10-8 M (for the phenytoin derivative) and 2.5×10-8 M (for the phenobarbital derivative) for non-simultaneous detection. © 1998 John Wiley & Sons, Ltd.
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  • 88
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    Applied Organometallic Chemistry 12 (1998), S. 145-145 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 89
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    Applied Organometallic Chemistry 12 (1998), S. 67-75 
    ISSN: 0268-2605
    Keywords: organotin ; tributyltin ; tributyltin oxide ; tetrabutyltin ; degradation ; bioassay ; bioindicator ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The growth response of the alga Chlorella kessleri and the euglenoid Euglena gracilis has been studied as a model system to determine the effects of a tin salt (SnCl4·5H2O) and of some organotin (OT) derivatives, namely tetrabutyltin (TeBT), tributyltin (TBT) and tributyltin oxide (TBTO). Abiotic degradation was studied as well. Cells were exposed to a toxicity series (0-50 μg/mL-1) for the four chemicals in seven-day bioassays. Both microorganisms are tolerant of the inorganic salt, but growth inhibition was significant for all OT compounds, and especially large for TBT and TBTO. Although C. kessleri and E. gracilis are known to be tolerant towards metals and organic chemicals, the present results show that both are sensitive to organotin compounds: the inhibition of the growth was greater for C. kessleri. © 1998 John Wiley & Sons, Ltd.
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  • 90
    ISSN: 0268-2605
    Keywords: surfactants ; carbohydrate ; carbosilane ; silane ; wetting ; surface tension ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of carbohydrate surfactants bearing carbosilane, silane, polysilane and non-permethylated siloxane moieties is described. These surfactants consist of three structural elements: (1) a silicon-containing moiety, (2) a spacer and (3) a carbohydrate unit. Additionally two different types of mixed structures have been synthesized: (a) single-chained carbosilane-siloxane surfactants and (b) double-chained combinations of carbo- silanes, silanes and siloxanes. The wetting behaviour of the key intermediates, the allyl glycidyl derivatives, has been investigated by static surface tension (γlv, σ) and wetting tension (γsv-γsl, α) measurements on a non-polar perfluorinated surface (FEP® plate). The contact angles obtained for these pure liquids are not a linear function of the surface tension but depend on the polarity of the substructures. © 1998 John Wiley & Sons, Ltd.
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  • 91
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    Applied Organometallic Chemistry 12 (1998), S. 79-85 
    ISSN: 0268-2605
    Keywords: organic tellurium compounds ; polycondensation ; amino groups ; polyamides ; polyurea ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several new and known organic tellurium compounds containing amino groups (i.e. ArTeBr3, Ar2Te2 and Ar2Te, where Ar= 4-NH2C6H4, 2-NH2C6H4, 4-CH3CONHC6H4 or 2-NH2-5-NO2-C6H3) were prepared by reacting aminoarylmercury chlorides with tellurium tetrabromide in glacial acetic acid. Bis(4-aminophenyl) telluride and bis(2-amino-5-nitrophenyl) telluride were polymerized with aromatic and aliphatic diacid chlorides (i.e. terephthaloyl chloride and sebacoyl chloride), as well as with toluene di-isocyanate, leading to new organic tellurium polyamides and polyurea. All organic tellurium compounds and their condensation polymers were characterized by elemental analyses, IR, 1H and 13C NMR, and mass spectroscopy. The thermal stabilities of the resulting polymers were determined by thermogravimetric and derivative thermogravimetric techniques. © 1998 John Wiley & Sons, Ltd.
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  • 92
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    Applied Organometallic Chemistry 12 (1998), S. 87-97 
    ISSN: 0268-2605
    Keywords: antitumor ; metal complexes ; amine-carboxyborane ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The amine carboxyborane metal complexes, tetrakis - μ - (trimethylamine - boranecarbo - xylato)acetonitrile dicopper(II) and bis-μ- (morpholine-boranecarboxylato)zinc(II) dihydrate demonstrated cytotoxic activity against human Tmolt3, HeLa-S3 and MB-9812 cell growth.Tetrakis-μ-(trimethylamine-boranecarboxylato)-acetonitrile dicopper(II) and bis - μ - (morpholine - boranecarboxylato)zinc (II) dihydrate inhibited L1210 DNA, RNA and protein syntheses, with greatest inhibitory effects on DNA synthesis. The reduction in DNA synthesis correlates well with inhibition of de novopurine synthesis and the key enzymes involved in this pathway, i.e. IMP dehydrogenase and PRPP amido transferase. These compounds were also observed to induce DNA strand scission but did not appear to intercalate between base pairs of DNA, alkylate bases or cause cross-linking of the strands of DNA. Tetrakis-μ-(trimethylamine - boranecarboxylato)acetonitrile dicopper(II) also demonstrated the ability to inhibit L1210 DNA topoisomerase II activity. © 1998 John Wiley & Sons, Ltd.
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  • 93
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    Applied Organometallic Chemistry 12 (1998), S. 109-119 
    ISSN: 0268-2605
    Keywords: bioconcentration ; toxicity ; TBTCl ; tilapia ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acute toxicity (96 h) and bioconcentration experiments of tributyltin chloride (TBT) in tilapia were conducted in an aqueous solution with salinity of 15‰, and a toxicity mechanism has been suggested. The 96-h LC50 was 3.80 μg Sn l-1. Bioconcentration factors in different tissues increased in the order muscle〈gill〈viscera. Studies on the metabolism of TBT showed that it can be easily degraded to DBT (dibutyltin) in these tissues. Further degradation of DBT to MBT (monobutyltin) was much more difficult. A mesocosm was used for the first time to study the toxicity of TBT in tilapia. The result demonstrated that the TBT bioconcentration curve changed with the initial concentrations of TBT but the order of bioconcentration in the tissues did not change. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 19 Ill.
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  • 94
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 99-107 
    ISSN: 0268-2605
    Keywords: phenyltin ; model membrane ; hemolysis ; fluorescence ; 1H NMR ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phenyltin compounds are known to be biologically active. Their chemical structure suggests that they are likely to interact with the lipid fraction of cell membranes. Using fluorescence and NMR techniques, the effect of phenyltin compounds on selected regions of model lipid bilayers formed from phosphatidylcholine was studied. The polarization of N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) dipalmitoyl-L-phosphatidylethanolamine and desorption of praseodymium ions was used to probe the polar region, whereas the polarization of 1 - (4 - trimethylammoniumphenyl) - 6 - phenyl - 1,3,5-hexatriene p-toluenesulfonate measured the hydrophobic core of the membrane. In addition, changes in the N-(5-fluoresceinthiocarbanoly)dipalmitoyl - L - α - phosphatidyl - ethanolamine fluorescence intensity indicated the amount of charge introduced by organotin compounds to the membrane surface. There were no relevant changes of measured parameters when tetraphenyltin was introduced to the vesicle suspension. Diphenyltin chloride causes changes of the hydrophobic region, whereas the triphenyltin chloride seems to adsorb in the headgroup region of the lipid bilayer. When the hemolytic activity of phenyltin compounds was measured, triphenyltin chloride was the most effective whereas diphenyltin chloride was much less effective. Tetraphenyltin causes little damage. Based on the presented data, a correlation between activity of those compounds to hemolysis (and toxicity) and the location of the compound within the lipid bilayer could be proposed. In order to inflict damage on the plasma membrane, the compound has to penetrate the lipid bilayer. Tetraphenyltin does not partition into the lipid fraction; therefore its destructive effect is negligible. The partition of the compound into the lipid phase is not sufficient enough, by itself, to change the structure of the lipid bilayer to a biologically relevant degree. The hemolytic potency seems to be dependent on the location of the compound within the lipid bilayer. Triphenyltin chloride which adsorbs on the surface of the membrane, causes a high level of hemolysis, whereas diphenyltin chloride, which penetrates much deeper, seems to have only limited potency. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 10 Ill.
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  • 95
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 121-128 
    ISSN: 0268-2605
    Keywords: MMT ; soils ; interactions ; Fourier-transform IR ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) and headspace analysis gas-phase infrared spectroscopy (HAGIS) were used to investigate interactions between soils and the gasoline additive methylcyclopentadienylmanganese tricarbonyl (MMT). Various soil samples, as well as alumina and silica substrates, were studied. Each substrate exhibited a splitting or broadening of the degenerate e ν(CO) band of MMT, suggesting an interaction involving one or two of the CO ligands. The adsorption was shown to be reversible under relatively mild conditions using HAGIS. The proposed interaction is of the Brønsted type, involving the carbonyl oxygen and a surface-bound water or hydroxyl group. This type of interaction could stabilize MMT by inhibiting photo-ejection of CO ligands, a common first step in the decomposition of organometallic carbonyl compounds such as MMT. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 5 Ill.
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  • 96
    ISSN: 0268-2605
    Keywords: trimethylantimony ; molecular rearrangement ; demethylation ; speciation ; hydride generation ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The method of hydride generation for the speciation of antimony compounds was examined with respect to the problem of molecular "rearrangement'. Specifically, demethylation of trimethylstilbine during the analysis of trimethylantimony dichloride (Me3SbCl2) was studied. Previously published observations that enhanced demethylation takes place as a result of inadequate preconditioning of the analytical apparatus were found to be not reproducible. However, demethylation was enhanced as the pH decreased when using two different analytical methods: semi-continuous flow hydride generation-gas chromatography-atomic absorption spectrometry (HG- GC-AAS), and batch-type hydride generation- gas chromatography-inductively coupled plasma mass spectrometry (HG-GC-ICP MS). Applications of the hydride generation method to environmental samples revealed differences in analytical results at high and low pH, and enhanced demethylation taking place because of the matrix in a fungal extract sample. The authors recommend that researchers using the method of hydride generation for antimony compounds carefully test the reaction conditions with standard compounds and use the method of standard addition only. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
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  • 97
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 145-145 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
    Type of Medium: Electronic Resource
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  • 98
    ISSN: 0268-2605
    Keywords: arsenobetaine ; arsenocholine ; trimethylarsine oxide ; tetramethylarsonium iodide ; organic arsenic compound ; arsenite ; arsenate ; marine organisms ; cytotoxicity ; chromosomal aberration ; sister chromatid exchange (SCE) ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Arsenobetaine, arsenocholine, trimethylarsine oxide and tetramethylarsonium iodide, which are contained in marine fishery products, were examined for their potencies on cell growth inhibition, chromosomal aberration and sister chromatid exchange (SCE). Arseno- betaine, the major water-soluble organic arsenic compound in marine animals, exhibited very low cytotoxicity towards mammalian cells. This compound showed no cell growth inhibition at a concentration of 10 mg cm-3 and the cytotoxicity was lower than 1/14 000th of that of sodium arsenite and 1/1600th of that of sodium arsenate towards BALB/c 3T3 cells. The chromosomal aberrations caused by arsenobetaine at a concentration of 10 mg cm-3 consisted mainly of chromatid gaps and chromatid breaks, but in this concentration chromosomal breakage owing to its osmotic pressure is likely to be considerable. No SCE was observed at a concentration of 1 mg cm-3. Arsenocholine and trimethylarsine oxide also showed no cell growth inhibited at a concentration of 10 mg cm-3. However, tetramethylarsonium iodide inhibition the growth of BALB/c 3T3 at a concentration of 8 mg cm-3. These compounds exhibited a low ability to induce chromosomal aberrations at a concentration range of 2-10 mg cm-3 and no SCE was observed at a concentration of 1.0 mg cm-3. These results suggested that the major and minor organic arsenic compounds contained in marine fishery products are much less cytotoxic inorganic arsenic, methylarsonic acid and dimethylarsinic acid. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
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  • 99
    ISSN: 0268-2605
    Keywords: laser-assisted chemical vapor deposition ; SnO2 ; SnBr4 ; copper(II) acetate ; gas sensors ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Laser-assisted chemical vapor deposition (LCVD) was utilized to produce SnO2 films from SnBr4 plus air, O2 or N2O. SnO2 films were successfully generated using either 222 or 308 nm laser pulses but there was evidence for film contamination when using less than 60 mJ/pulse laser energies at 222 nm. Films were characterized using ultraviolet absorption spectroscopy; the spectra of films with impurities resembled the spectrum of SnBr4. AFM images were obtained which indicated that this LCVD route produced small and fairly uniform SnO2 grains which were 50-100 nm in size. Multiphoton ionization spectroscopy was used to verify that the dissociation of a film dopant precursor, copper(II) acetate, produced gas-phase copper atoms under conditions similar to those used in film deposition experiments. The deposition of SnO2 from SnBr4 plus an oxidant was found to be more efficient than from di-n-butyl tin diacetate but films produced via this new LCVD route, including those doped with copper, were found to be much less sensitive in preliminary gas-sensing screening. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 7 Ill.
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  • 100
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 155-160 
    ISSN: 0268-2605
    Keywords: tungsten trioxide ; electrochromism ; thin films ; chemical vapor deposition (CVD) ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Crystalline and amorphous thin films of tungsten(VI) oxide can be prepared by chemical vapor deposition using a variety of volatile precursors below 500 °C. Deposition parameters for preparation of WO3 films from tungsten hexacarbonyl [W(CO)6], tungsten hexafluoride (WF6), tungsten ethoxides [W(OEt)x, x = 5, 6] and tetra(allyl)tungsten [W(η3-C3H5)4] are summarized. The electrochromic behavior of these films is comparable with that observed for WO3 films prepared by evaporation, sputtering and electrodeposition. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
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