摘要:

AbstractThe kinetics of base hydrolysis of (αβ S)‐(o‐methoxy benzoato) (tetraethylenepentamine)cobalt(III) obeyed the rate law:kobs=kOH[OH−], in the range 0.05 ⩽ [OH−]T, mol dm−3⩽ 1.0, I = 1.0 mol dm−3, and 20.0–40.0°C. At 25°C,kOH= 13.4 ± 0.4 dm3mol−1s−1, ΔH≠= 93 ± 2 kJ mol−1and ΔS≠= 90 ± 5 JK−1mol−1. Several anions of varying charge and basicity, CH3CO2−, SO32−, SO42−, CO32−, C2O42−, CH2(CO2)22−, PO43−, and citrate3−had no effect on the rate while phthalate2−, NTA3−, EDTA4−, and DTPA5−accelerated the process via formation of the reactive ion pairs. The anionic (SDS), cationic (CTAB), and neutral (Triton X‐100) micelles, however, retarded the reaction, the effect being in the order SDS>CTAB>Triton X‐100. The importance of electrostatic and hydrophobic effects of the micelles on the selective partitioning of the reactants between the micellar and bulk aqueous pseudo‐ph

ISSN:0538-8066    

DOI:10.1002/kin.550260702

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe nature of interaction of Co(III) complexes such as Co(III)EDTA and Co(III)NTA with transient adducts of thymine such as TOH˙, T˙−, and TH˙formed in the gamma radiolysis of thymine were studied. The study shows that TOH radicals do not undergo electron transfer reaction with Co(III) complexes whence no radiosensitization of thymine by Co(III) complexes was observed. Electron transfer however, takes place from T˙−and TH˙to Co(III) complexes. A plausible mechanism of radiolysis of thymine in presence of Co(III) complexes is discussed. © 1994 John Wiley&

ISSN:0538-8066    

DOI:10.1002/kin.550260703

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe multiphoton decomposition of CF3I with a pulsed CO2laser has been studied at incident fluences of 0.6 and 1.2 J/cm2. The effect of pressure on the reaction probability for dissociation of CF3I was measured in the presence of added isobutane, Ar and CO2. In the experiments with isobutane, the CF3radicals generated by the decomposition of excited CF3I react to yield CF3H in competition with the recombination to C2F6. The laser absorption cross section was also measured as a function of fluence at a pressure of 0.1 torr of CF3I and with 0.5–2.0 torr of added isobutane. The experimental results were modeled with a master equation in order to obtain information on the energy transferred by collisions of excited CF3I with the bath molecules. An energy dependent value of 〈ΔE〉dproduces the best fit to the experimental data. Integration of the rate equations to account for the fractional product yield, [CF3I]/[C2F6], allowed for the calculation of the specific rate constant for hydrogen abstraction from isobutane by CF3radicals. The value obtained is dependent on the total pressure and higher than expected at room temperature. From these results, an effective temperature for the reaction mixture was calculated. © 1994 John Wiley&So

ISSN:0538-8066    

DOI:10.1002/kin.550260704

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe rate coefficients for the reactions of Cl atoms with CH3Br, (k1) and CH2Br2, (k2) were measured as functions of temperature by generating Cl atoms via 308 nm laser photolysis of Cl2and measuring their temporal profiles via resonance fluorescence detection. The measured rate coefficients were:k1= (1.55 ± 0.18) × 10−11exp{(−1070 ± 50)/T} andk2= (6.37 ± 0.55) × 10−12exp{(−810 ± 50)/T} cm3molecule−1s−1. The possible interference of the reaction of CH2Br product with Cl2in the measurement ofk1was assessed from the temporal profiles of Cl at high concentrations of Cl2at 298 K. The rate coefficient at 298 K for the CH2Br + Cl2reaction was derived to be (5.36 ± 0.56) × 10−13cm3molecule−1s−1. Based on the values ofk1andk2, it is deduced that global atmospheric lifetimes for CH3Br and CH2Br2are unlikely to be affected by loss via reaction with Cl atoms. In the marine boundary layer, the loss via reaction (1) may be significant if the Cl concentrations are high. If found to be true, the contribution from oceans to the overall CH3Br budget may be less than what is currently assumed. ©

ISSN:0538-8066    

DOI:10.1002/kin.550260705

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractClassical trajectory calculations on the methyl isocyanide molecule at energies above 25,000 cm−1confirm that the rate of reaction to methyl cyanide is bimodal, with a very fast rate before 0.1 ps, and a slower rate from then on. We conclude that before 0.1 ps, the reacting molecules are unrandomized, but thereafter, they are essentially randomized, with decay to products being, to a good approximation, pure exponential. We estimate that the time for randomization is roughly 0.3 ps at energies near the reaction threshold of 13,500 cm−1. © 1994 John Wiley&Sons,

ISSN:0538-8066    

DOI:10.1002/kin.550260706

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe dissolution and the kinetics of dissolution of cooper(II) oxide in water saturated by sulphur dioxide has been studied. In the experiments, the particle size, the flow rate of the gas, the solid to liquid ratio, and the reaction temperature have been chosen as parameters, while the stirring rate was held constant. As a result of present experiments, it was observed that the decrease of the particle size, the solid to liquid ratio, and an increase of the reaction temperature increased the dissolution rate. It was also observed that the flow rate of sulphur dioxide in the range of its flow rate values did not affect the dissolution rate.The reaction kinetics of copper(II) oxide according to the heterogeneous reaction models was examined and it was found that the dissolution rate was controlled by chemical reaction. The calculated activation energy is 66.50 kJmol−1. © 1994 John Wiley&Sons, I

ISSN:0538-8066    

DOI:10.1002/kin.550260707

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractAn exceptional kinetic behavior on the reactivity of β‐diketones against copper(II) have been found. Some relationship between ligand basicity and unexpected enhancement on the rates of complex formation, which may be useful for predicting rate constants of similar monochelated copper(II) complexes, are established. © 1994 John Wiley&Sons,

ISSN:0538-8066    

DOI:10.1002/kin.550260708

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe new flowtube reactor employing dissociative electron attachment to produce radicals and high‐pressure photoionization in the mass spectrometric detection of radicals is described. The system has been applied to a study of the association reactions of CHCl2and CCl3with O2in a great excess of helium at total densities below 1017cm−3over the temperature range 286 to 332 K. Both reactions display a strong negative temperature coefficient. The results can be parameterized in the formk0(CHCl2+ O2) = (4.3 ± 0.2) × 10−31(T/300)−6.7±0.7cm6s−1,k0(CCl3+ O2) = (2.7 ± 0.2) × 10−31(T/300)−8.7±1.0cm6s−1. © 199

ISSN:0538-8066    

DOI:10.1002/kin.550260709

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractIgnition of propane has been studied in a shock tube and by computational modeling to determine the effect of methyl tert‐butyl ether (MTBE) as a fuel additive. MTBE and isobutene were added in amounts up to 25% of the fuel to propane‐oxygen‐argon mixtures in shock tube experiments covering a range of temperatures between 1450 and 1800 K. Ignition delays were measured from chemiluminescence at 432 nm due to excited CH radicals. The temperature dependence of the ignition rates was analyzed to yield Arrhenius parameters ofEaca. 40 kcal/mol andAca. 109s−1for the overall propane reaction andEaca. 34 kcal/mol andAca. 108.3s−1for the overall propane/MTBE reaction. Reactions involving MTBE and its decomposition products were combined with an established propane mechanism in a numerical model to describe the kinetic interaction of this additive with a typical hydrocarbon fuel. The experiments and the kinetic model both show that MTBE and isobutene retard propane ignition with nearly equal efficiency. The kinetic model demonstrates that isobutene kinetics are responsible for inhibition by both MTBE and isobutene, and the specific elementary reactions that produce this behavior are identified. © 1994 John Wiley

ISSN:0538-8066    

DOI:10.1002/kin.550260710

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe rate constants for the reaction of C6H5with HBr and DBr have been measured with the cavity–ring–down method in the temperature range of 297 to 523 K and 297 to 500 K, respectively. These rate constants can be effectively represented, in units of cm3/s, by\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} k_{{\rm HBr}} = 10^{- 10.40 \pm 0.24} \exp \left[{{{\left({- 554 \pm 208} \right)} \mathord{\left/ {\vphantom {{\left({- 554 \pm 208} \right)} T}} \right. \kern-\nulldelimiterspace} T}} \right]{\rm and} \\ k_{{\rm DBr}} = 10^{- 10.36 \pm 0.17} \exp \left[{{{\left({- 662 \pm 151} \right)} \mathord{\left/ {\vphantom {{\left({- 662 \pm 151} \right)} T}} \right. \kern-\nulldelimiterspace} T}} \right]{\rm.} \\ \end{array} $$\end{document}Both activation energies are similar and positive, contrary to those of alkyl radical reactions, all of which exhibit negative temperature dependencies. The difference, as pointed out before [1], could be accounted for by the electron‐withdrawing effect of the phenyl vis‐à‐vis the electron‐donating ability of the alkyls. © 1994 John Wi

ISSN:0538-8066    

DOI:10.1002/kin.550260711

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY