摘要:

AbstractUsing a laser pyrolysis/laser fluorescence method, we have measured the rate constants for OH reacting with 1‐butene,t‐2‐butene, isobutene, and 2,3‐dimethyl‐2‐butene near 1200 K. The butene rate constants are large, ranging from 2.0–3.7 × 10−11cm−3s−1, and increase with the number of allylic hydrogens. Transition‐state theory considerations indicate these allylic hydrogens are easily abstracted, in contrast to prior o

ISSN:0538-8066    

DOI:10.1002/kin.550190402

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractKinetics and mechanism of the cerium(IV) oxidation of Cr(III) complexes of a series of macrocyclic (or pseudomacrocyclic) ligands with [14]‐membered intraligand ring‐sizes have now been investigated atI= 1.0 M (LiClO4) Temp. 30°C. The complexes of the formulation Cr(macrocycle)(X)(H2O) (3−n) +whereX= CHCl2and H2O,n= 0 or 1 undergo oxidation to Cr(VI) with the formation of chromium(IV) intermediates. The observed kinetic parameters for the Ce(IV) oxidation of Cr(III) macrocyclic complexes have been discussed in terms of changes brought about by the macrocyclic ligands on the Cr(III)—Cr(IV) redox potentials and in specific rates for Cr(IV)—Cr(V) conversion. On the basis of this study, it has been suggested that the trapping of Cr(IV) is easier when a macrocyclic ligand having a symmetrical intra‐ligand ring size and unsaturation in the cyclic structure is coordinated equatorially. Cyclic voltammetric studies indicate the formation of Cr(IV) transient in the case of electrochemical oxidation oftrans‐Cr(Me4[14]

ISSN:0538-8066    

DOI:10.1002/kin.550190403

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractRate constants for the gas‐phase reactions of NO3radicals with a series of alkynes, haloalkenes, and α,β‐unsaturated aldehydes have been determined at 298 ± 2 K using a relative rate technique. Using rate constants for the reactions of NO3radicals with ethene and propene of (1.1 ± 0.5) × 10−16cm3molecule−1s−1and (7.5 ± 1.6) × 10−15cm3molecule−1s−1, respectively, the following rate constants (in units of 10−16cm3molecule−1s−1) were obtained: acetylene, ≤0.23; propyne, 0.94 ± 0.44; vinyl chloride, 2.3 ± 1.1; 1,1‐dichloroethene, 6.6 ± 3.1;cis‐1,2‐dichloroethene, 0.75 ± 0.35;trans‐1,2‐dichloroethene, 0.57 ± 0.27; trichloroethene, 1.5 ± 0.7; tetrachloroethene,<0.4; allyl chloride, 2.9 ± 1.3; acrolein, 5.9 ± 2.8; and crotonaldehyde, 41 ± 9. The atm

ISSN:0538-8066    

DOI:10.1002/kin.550190404

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractAbsolute rate constants have been measured for the reactions of trichloromethylperoxyl radicals with cyclohexane, cyclohexene, and hexamethylbenzene. The CCl3O2radicals were produced by pulse radiolysis of air‐saturated CCl4solutions containing various amounts of the hydrocarbons. The rate constants were determined by competition with the one‐electron oxidation of metalloporphyrins, using the rate of formation of the metalloporphyrin radical cation absorption to monitor the reaction by kinetic spectrophotometry. The rate constants for hydrogen abstraction from cyclohexane, cyclohexene, and hexamethylbenzene were found to be 1 × 103, 1.0 × 105, and 7.5 × 104M−1s−1, re

ISSN:0538-8066    

DOI:10.1002/kin.550190405

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractExperimental data for the reaction of O atoms with NH3have been reviewed with particular attention to the possible effects of secondary reactions on the deduced rate coefficient. A reaction mechanism was assembled and computer calculations carried out to simulate several sets of experiments. The sensitivity of the calculations to uncertainties in the various rate coefficients was assessed. Transition‐state theory calculations were carried out on the rate coefficientk1for the O + NH3→ OH + NH2reaction. These studies suggest that the reaction stoichiometry is dependent on temperature, initial reagent ratios, and extent of reaction; that available data are not sufficient to determine whether the initial step is H‐atom abstraction (producing OH and NH2radicals) or O‐atom addition (producing an NH3O* complex): and that the low temperature values ofk1(T⩽ 400 K) are not consistent with values deduced at higher temperatures if the reaction proceeds by H‐atom abstraction. Taking all the evidence into account, it is recommended that the expression 1.1 × 103T2.1exp(−2620/T) L mol−1s−1be used fork1until more definitive experimental measurements are made a

ISSN:0538-8066    

DOI:10.1002/kin.550190406

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe kinetics of the Diels‐Alder additions of CH2= CHCN, CH2= C(CH3) CN, andcis‐ andtrans‐CH3CH = CHCN to cyclohexa‐1, 3‐diene have been studied in the gas phase. The stereochemistry of these reactions is discussed. In terms of a biradical mechanism, a minimum value of 4.1 ± 0.8 kcal mol−1for the stabilizing effect of a CN groupvis‐à‐visa methyl group is shown to fit the experimental ac

ISSN:0538-8066    

DOI:10.1002/kin.550190407

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe average downward energy transfer (〈ΔEdown〉) is obtained for highly vibrationally excited acetyl chloride with Ne and C2H4bath gases at ca. 870 K. Data are obtained by the technique of very low‐pressure pyrolysis (VLPP). Fitting these data by solution of the appropriate reaction‐diffusion integrodifferential master equation yields the gas/gas collisional energy transfer parameters: 〈ΔEdown〉 values are 220 ± 10 cm−1(Ne bath gas) and 330 ± 20 cm−1(C2H4).These energy transfer quantities are much less than those predicted by statistical theories, or those observed for similar sized molecules such as CH3CH2Cl. These results are explained by the qualitative predictions of the biased random walk model wherein the fundamental mechanism of energy transfer is the multiple interactions between the bath gas and the individual atoms of the reactant molecule, during the course of the collision event. The charge distribution of acetyl chloride decreases the number of such interactions, thereby reducing the amount of energy transf

ISSN:0538-8066    

DOI:10.1002/kin.550190408

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550190401

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY