摘要:

AbstractCF3BrH2mixtures highly diluted with Ar were studied by using a time‐resolved IR‐emission of HBr and a gas‐chromatography for reaction products. The temperature range covered was 1000–1600 K and the total pressure behind the reflected shock waves used was 1.2–2.6 atm. CF3H, C2F6, and C2F4were produced and the yields of these products were determined as a function of temperature. The main product under our experimental conditions was CF3H. The mechanism and the rate constants of CF3BrH2reaction at high temperatures were discussed. The experimental data was satisfactorily modeled using a 14‐reaction mechanism. Reaction (5) played an important role in the formation of CF3H together with reaction (4).The rate constant expressionk5= 2.2 × 1013exp(−12 kcal/RT) cm3mol−1s−1gave the best agreement between the calculated and observed results. © 19

ISSN:0538-8066    

DOI:10.1002/kin.550251202

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractA kinetic study of the decomposition reactions ofN‐bromoalanine,N‐bromo‐2‐aminobutyric acid, andN‐bromonorvaline shows them to be first‐order with respect toN‐bromoaminoacid concentration and independent of both excess aminoacid and pH over the interval pH 9–11. In this pH range the mean rate constants at 298 K were 1.20 × 10−3s−1, 1.37 × 10−3s−1and 1.28 × 10−3s−1, respectivel

ISSN:0538-8066    

DOI:10.1002/kin.550251203

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe kinetics and mechanism of the reaction of complexation of iron(III) with 2,4‐octanedione and 2,4‐nonanedione have been investigated spectrophotometrically in aqueous solution at 10°C and ionic strength 0.5 mol dm−3NaClO4. The equilibrium constants of the mono‐complexes have been determined. The mechanism proposed to account for the kinetic data involves a double reversible pathway where both Fe3+and Fe(OH)2+react with the enol tautomer of the ligand. 2,4‐Octanedione reacts with Fe3+and Fe(OH)2+with rate constants of 0.65 dm3mol−1s−1, and 14.07 dm3mol−1s−1, respectively. For 2,4‐nonanedione complexation the rate constants determined are 0.49 dm3mol−1s−1, and 11.39 dm3mol−1s−1, respectively. Some discussions are made on the basis of Eigen‐Wilkins theory considering the effect of solvent exchange on the complex formatio

ISSN:0538-8066    

DOI:10.1002/kin.550251204

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractA large rate increase of the oxidation of hydroxylamine by iodate has been shown in frozen aqueous solution as compared to the supercooled one. The experiments were conducted under frozen conditions at −5°, −10°, −15°, and −20°C and in liquid solution at 0°, −5°, and −10°C, as well. At given time intervals the progress of the reaction was traced by the pH decrease of the unbuffered samples. The around 500‐fold enhanced reaction rate of the frozen samples (at −5° and −10°C) points to an important role of the ice itself beside the increased solute concentration in the compartmentalized heterogeneous system. The contribution of ice to this pH‐regulated oxidation is discussed as a consequence of the high mobility and transfer rate of proton on the ice surface.

ISSN:0538-8066    

DOI:10.1002/kin.550251205

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe thermal isomerization ofcis‐hexatriene (cHT) to cyclohexadiene (CHD) and the dimerization of CHD andtrans‐hexatriene (tHT) in the liquid phase in the temperature range 380 K‐473 K are reported.The rate coefficients are: for thecHT to CHD isomerization\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_2 = - (27,500 \pm 1500)/4.567T + (10.7 \pm 0.5)(s^{ - 1}) $$\end{document}fortHT dimerizationlog\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_{3a} = - (23,100 \pm 300)/4.576T + (7.6 \pm 0.1){\rm }lmol^{ - 1} s^{ - 1} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_{3b} = - (22,400 \pm 1000)/4.576T + (7.6 \pm 0.1){\rm }lmol^{ - 1} s^{ - 1} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_{3c} = - (20,600 \pm 1500)/4.576T + (6.4 \pm 0.1){\rm }lmol^{ - 1} s^{ - 1} $$\end{document}and for CHD dimerization; endo form\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_{5a} = - (23,200 \pm 1500)/4.576T + (6.1 \pm 0.2){\rm }lmol^{ - 1} s^{ - 1} $$\end{document}exo form\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_{5b} = - (25,400 \pm 1500)/4.576T + (6.5 \pm 0.2){\rm }lmol^{ - 1} s^{ - 1} $$\end{document}© 1993 John Wiley&Son

ISSN:0538-8066    

DOI:10.1002/kin.550251206

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractKinetic absorption spectroscopy is a commonly used technique in the experimental determination of rate constants. Here we consider the effect of nonuniform reactant concentrations upon the measured results and the errors associated with the final determination of second‐order rate constants in particular. We conclude that the errors associated with nonuniformity of reactant, while significant, are comparable or less than other common systematic or random errors. © 1993 John Wiley&Sons, I

ISSN:0538-8066    

DOI:10.1002/kin.550251207

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

Abstract1,5‐cyclooctadiene or 4‐vinylcyclohexene mixture diluted with argon was heated to temperatures in the range 880–1230 K behind reflected shock waves. Profiles of IR‐laser absorption were measured at 3.39 μm. From these profiles, rate constantsk1andk2for the decyclization reactions 1,5‐cyclooctadiene → biradical and 4‐vinylcyclohexene → biradical were evaluated ask1= 5.2 × 1014exp(−48.3kcal/RT) s−1andk2= 3.5 × 1014exp(−55.3kcal/RT) s−1, respectively.

ISSN:0538-8066    

DOI:10.1002/kin.550251208

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractAlkylation of 5‐phenyltetrazole with isopropyl alcohol in 84–99% sulfuric acid medium occurs regioselectively at N2 position of the heterocycle to produce 2‐isopropyl‐5‐phenyltetrazole. The regioselectivity is conditioned by 1H, 4H‐5‐phenyltetrazolium cation being the alkylation substratum. The reaction mechanism is proved to be two‐stage one. Its first and rate‐limiting stage is an interaction between the azolium cation and isopropyl cation generated from protonated isopropyl alcohol. The reaction rate constant was estimated as 0.47 L mol−1s−1at 25°C. Water activity scale was used for quantitative description of equilibrium of isopropyl cation formation from the protonated alcohol, and the equilibrium constant pKR+= −5.3 was evaluated from the data of the alkylation kinetics. ©

ISSN:0538-8066    

DOI:10.1002/kin.550251209

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractAbsolute rate constants were measured for the reaction CN + CH2O over the temperature range 297–673 K and CN + 1,3,5‐trioxane over the range of 297–600 K by the laser photolysis/laser induced fluorescence technique. The rate constants for these reactions can be effectively represented, in units of cm3/s, by:k(CH2O) = 2.82 × 10−19T2.72exp(718/T), andk(1,3,5‐trioxane) = 1.39 × 10−23T4.26exp(1333/T), respectively. Transition state theory calculations were able to fit the temperature dependence of the CN + CH2O rates relatively well. We attempted to correlate the CN reaction rate with CH2O and other molecules which occur through simple abstraction with the corresponding OH reaction rates, yielding only a qualitative linear correlation for a majority of the processes. The reactions which deviated significantly from linearity include those which contain strong dipoles, highlighting the significant role long‐range attractive forces play in CN and OH reactions. Using a simple electrostatic potential, cross‐sections were determined for reactions with CN. No linear correlation was found between the calculated and experimental cross sections for the majority of the reactions studied. © 1993 Jo

ISSN:0538-8066    

DOI:10.1002/kin.550251210

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550251201

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY