ISSN:0538-8066    

DOI:10.1002/kin.550130902

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550130903

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractAn approximate analytical solution of relaxation in a low‐pressure system with exponential transition probabilities is given for vibrational–rotational energy transfer in the dissociation of diatomics. The main assumption is that the rotational degrees of freedom are in thermal equilibrium at all times, and that the barrier to dissociation in the vibrational–rotational plane is linear and asymmetric. The theory is applied to high‐temperature dissociations of N2, Br2, and CO in excess argon, with satisfactory agreement with available experiment

ISSN:0538-8066    

DOI:10.1002/kin.550130904

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractH atoms react with C2H5SSC2H5to give C2H5SH as the sole retrievable product with ϕ = 2.32 at 25°C and 2.84 at 145°C. The primary reaction is postulated to be H + C2H5SSC2H5← C2H5SH + C2H5S withk1= (4.73 ± 0.64) × 1013exp [−(1710 ± 69)/RT] cm3/mol·s relative to the rate constant of the H + C2H4← C2H5reaction. The high value of the entropy of activation suggests the presence of partial hydrogen bonding in diethyldisulfide which is broken in the transition state.Ethylmethyldisulfide reacts similarly: H + C2H5SSCH3← C2H5SH + CH3S or CH3SH + C2H5S. The thiyl radicals propagate a chain of radical exchange reactions forming the symmetrical disulfides with exposure‐time‐dependent quantum yields. The overall kinetics conform to a 16‐step mechanism from which the rate constants of the elementary reactions could be established by computer modeling. Thiyl radicals react considerably more slowly with dis

ISSN:0538-8066    

DOI:10.1002/kin.550130905

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractMethyl nitrate decomposition is accompanied by self‐heating. Using very fine thermocouples, direct measurements of excess temperatures have been made to establish the intensity and extent of self‐heating in nonisothermal reaction. The measurements are displayed as contourlines of equal degrees of temperature excess on the pressure–temperature ignition diagram.A twofold kinetic investigation has been made of the overall reaction. One part concentrates on achieving isothermal conditions and full characterization of intermediate products. It uses mass‐spectrometric analyses both to establish stoichiometry throughout decomposition and to validate velocity constant measurements derived from continuous pressure–time records. The best value forE= 151 ± 3 kJ/mol is about 10 kJ/mol less than previously.The other part deliberately invades the nonisothermal region to test the qualitative and quantitative predictions of theory (1) that uncorrected reaction orders and activation energies will exceed their isothermal values, (2) that their relative excess (δn/n, δE/E) will be about the same, and (3) that they will be dependent in a simple and predictable way on the reduced excess central

ISSN:0538-8066    

DOI:10.1002/kin.550130906

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractArrhenius parameters for the decomposition reactions of various alkoxy radicals are evaluated. The recommended values fortert‐butoxy radical decomposition reaction are logA(s−1) = 14.1,Ea= 15.3 kcal/mol.The parameters give reasonably self‐consistent results with related rate constants, product distributions of hydrocarbon oxidation reactions, and the values reported in different laboratories in different environments.A reworking of data by Batt et al. on RO + NO and RO + NO2leads to a lowering of hisAfactors for these reactions by a factor of 5. It also leads to a similar lowering of theAfactors for RO decompositions. The intrinsic activation energiesEfor the addition of alkyl radicals R to the carbonyl group are not only found to be a function of the exothermicity of reaction, but they are also dependent on the nucleophilicity of the alkyl radicals. For each radical R (Me, Et,i‐Pr) the data can be fit to an Evans–Polanyi plotE=a+b(δH), where a uniform slopeb= 0.58 can be found for all R. The interceptsaare then found to decrease nearly linearly with the decreasing ionization potential of R, namely,a= 2.1 [IP] – 6.2 (kcal/mol), with the ionization potential given in el

ISSN:0538-8066    

DOI:10.1002/kin.550130907

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractA preliminary report is given of relative reactive cross sections for four abstraction reactions H + H′Br ← HH′ + Br with attacking atom (A) H or D, and atom under attack (B) H or D. The pattern of reactive cross sections, as obtained in a crossed molecular beam experiment at a collision energyET= 7 kcal/mol, indicatesSr(D,H) ≤Sr(D,D)>Sr(H,H)>Sr(H,D). The atoms in parentheses are A and B. We describe a three‐dimensional classical trajectory (CT) study on a potential‐energy surface proposed in 1969 by Parr and Kuppermann (PK); the CT results are in fair accord with experiment. It is suggested that (D,H) has the largest cross section because it exhibits the most favorable relative timing of A approach to BC rotation. On the basis of CT it appears that the same sequence of cross sections and the same rationale may be applied to the exchange reactions H + BrH

ISSN:0538-8066    

DOI:10.1002/kin.550130908

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractWith a continuous jet‐stirred tank reactor operating at small space time (0.05–1.2 s) the kinetics of the formation of six minor products (ethane, isobutane, butene‐1, 2,3‐dimethyl‐butane, 4‐methylpentene‐1, and 1,5‐hexadiene) are studied during the pyrolysis of propane, at small extents of reaction and over the temperature range of 600–780°C. The experimental results are in agreement with the free radical mechanism proposed by Jezequel, Baronnet, and Niclause for this reaction. They show that the two most important termination processes areThe measured rates of formation of the minor products are consistent with the quasi‐identical values estimated by Jezequel and co‐workers (between 475 and 505°C) and by Allara and Edelson (between 510 and 560°C) for kinetic parameters (A1≃ 1016.65s−1andE1≃ 84.7 kcal/mole)

ISSN:0538-8066    

DOI:10.1002/kin.550130909

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractConsideration of current information on the dependence of the electron transfer rate on the radial separation distance and on the reactants′ radial distribution function suggests for adiabatic transfers a frequency factor closer to 1012M−1s−1than to 1011M−1s−1. One effect is to raise the λ values estimated from self‐exchange rate constants, and to extend thereby the range of ΔG°'s in which the “inverted region′” is masked by a diffusion‐co

ISSN:0538-8066    

DOI:10.1002/kin.550130910

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractCFBr radicals produced by the reaction of atomic oxygen with F2CCFBr were monitored in a discharge flow system by fluorescence excited at 424 nm. The rate coefficients for reactions of the CFBr radicals were measured between 298 and 358 K, and the following values were obtained in units of cm3/molec·s: O2<2 × 10−16at 353 K; NO<10−14at 298 K; F2CCFBr<10−15at 298 K; Cl2(1.9 ± 0.6) × 10−12exp(−762 ± 92/T) Br2(1.4 ± 0.3) × 10−

ISSN:0538-8066    

DOI:10.1002/kin.550130911

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY