摘要:

AbstractA detailed statistical study is presented, based on simulated experimental data, on the estimation of activation parameters using the Arrhenius equation:k=Aexp(B/T). The close correlation of the two parameters is shown, which requires the computation of the covariance matrix for the representation of uncertainties. This matrix facilitates the correct estimation of the confidence interval for interpolated (or extrapolated) values of rate coefficients. It is proposed that the full correlation matrix should be published in any article dealing with the determination of Arrhenius parameters.The importance of correct weighting is emphasized. Nonlinear fitting to the Arrhenius equation can be carried out without weighting only in case the (absolute) error of rate coefficient is independent of the temperature. Simulated experiments show that noncorrect weighting shifts the average values of fitted parameters and increases the variance of the parameters as well.With respect to the modified Arrhenius equation:k=A·Tnexp(B/T), statistical analysis shows that the physically meaningful estimation of all three parameters is impossible. Nonlinear fitting of three parameters is suggested for interpolation (and extrapolation) of rate coefficients, whereas in case of activation parameter estimation, the fixing of “n” on the basis of theoretical considerations is advised followed by the estimation of the remaining two parame

ISSN:0538-8066    

DOI:10.1002/kin.550190302

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe pyrolysis of 4‐chloro‐1‐butanol has been studied in a static system, seasoned with allyl bromide, and in the presence of the free radical suppressor toluene. The working temperature and pressure ranges were 400–450°C and 43–164 Torr, respectively. The reaction is homogeneous, unimolecular, and follows a first‐order rate law. The temperature dependence of the rate coefficients is given by the following Arrhenius equation: logk1(s−1) = (13.34 ± 0.50) − (221.1 ± 6.7) kJ mol−1(2.303RT)−1. The products tetrahydrofuran, formaldehyde, and propene, arise by the participation of the neighboring OH group in 4‐chloro‐1‐butanol pyrolysis. The reaction is best explained in terms of an intimat

ISSN:0538-8066    

DOI:10.1002/kin.550190303

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe gas phase reaction of N2O5with water vapor was investigated in a 17.3‐m3Teflon lined chamber. Temporal concentration profiles for ozone, total nitrogen oxides, and nitrogen dioxide were measured. Concentration profiles for N2O5and HNO3were calculated from a combination of measurements of nitrogenous species. A kinetic mechanism with an adjustable value for the rate constant of N2O5+ H2O was used to model the experiments. From this analysis an upper limit value ofk⩽ 4 × 10−7ppm−1min−1for the gas phase reaction N2O5+ H2O → 2HNO

ISSN:0538-8066    

DOI:10.1002/kin.550190304

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractReactions which proceed through energized adducts, including radical recombinations, insertions, and addition to unsaturates, frequently exhibit unusual kinetic behavior. The branching ratios among various product channels are often complex functions of both temperature and pressure. Four such reactions involving methyl radicals are analyzed by combining chemical activation distribution functions with QRRK methods to predict rate constants for each channel. These include three oxidation paths, CH3+ O, CH3+ O2, CH3+ OH, and the addition reaction CH3+ C2H2. These predictions are compared to experiments wherever possible; generally, the agreement is quite satisfactory. Analysis of the energetics of the various reaction channels, using parameters which are readily available, provides a convenient framework for prediction. Suggested rate constants for the various channels for the four reactions are given at three pressures, 20, 760, and 7600 Torr, for the temperature range 300–2500 K. The approach used here can easily be applied to other reaction

ISSN:0538-8066    

DOI:10.1002/kin.550190305

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe direct photolysis of bicyclo[4.2.0]octa‐2,4‐diene in the gas phase at 280–300 nm produces mainly 1,3,5‐cyclooctatriene and benzene plus ethylene. The yield of the former product is enhanced by added gases, and it is proposed that it is formed in a vibrationally excited state which can revert to bicyclooctadiene unless the excess energy is removed in collisions. Computer modelling of the direct photolysis yielded quantitative agreement with the experimental results, but only when large, arbitrary adjustments were made to the calculated rate constants for the interconversion of cyclooctratriene and bicyclooctadiene. The Hg(63P1) sensitized reaction of bicyclooctadiene produces mainly benzene plus ethylene, a process which is also enhanced by adde

ISSN:0538-8066    

DOI:10.1002/kin.550190306

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe gas‐phase reaction of the NO3radical with NO2was investigated, using a flash photolysis‐visible absorption technique, over the total pressure range 25–400 Torr of nitrogen or oxygen diluent at 298 ± 2 K. The absolute rate constants determined (in units of 10−13cm3molecule−1s−1) at 25, 100, and 400 Torr total pressure were, respectively, (4.0 ± 0.5), (7.0 ± 0.7), and (10 ± 2) for M = N2and (4.5 ± 0.5), (8.0 ± 0.4), and (8.8 ± 2.0) for M = O2. These data show that the third‐body efficiencies of N2and O2are identical, within the error limits, and that previous evaluations for M = N2are applicable to the atmosphere. In addition, upper limits were determined for the rate constants of the reactions of the NO3radical with methanol, ethanol, and propan‐2‐ol of ⩽6 × 10−16, ⩽9 × 10−16, and ⩽2.3 × 10−15cm3mo

ISSN:0538-8066    

DOI:10.1002/kin.550190307

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractAbsolute rate coefficients for the reactions of the hydroxyl radical with dimethyl ether (k1) and diethyl ether (k2) were measured over the temperature range 295–442 K. The rate coefficient data, in the units cm3molecule−1s−1, were fitted to the Arrhenius equationsk1(T) = (1.04 ± 0.10) × 10−11exp[−(739 ± 67 cal mol−1)/RT] andk2(T) = (9.13 ± 0.35) × 10−12exp[+(228 ± 27 kcal mol−1)/RT], respectively, in which the stated error limits are 2σ values. Our results are compared with those of previous studies of hydrogen‐atom abstraction from saturated hydrocarbons by OH. Correlations between measured reaction‐rate coefficients and CH bond‐disso

ISSN:0538-8066    

DOI:10.1002/kin.550190308

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractA simple collision theory model for reaction between two different radicals shows that the cross‐reaction ratio, ϕ*, is 2 only if the masses and collision diameters of the radicals are identical; for all other combinations of mass and size, ϕ* is greater than 2. The value of ϕ* is shown to depend simply on the ratios of the masses and diameters of the two radicals: which of the two is the heavier or larger is unimportant.Calculated and experimental values of ϕ* are compared for several systems involving small alkyl and fluoroalkyl radicals, and the relationship between ϕ* and ϕ, the cross‐combination ratio, is

ISSN:0538-8066    

DOI:10.1002/kin.550190309

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550190301

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY