摘要:

AbstractGas‐phase rate constants for the reaction of NO2with 16 conjugated olefins were determined at room temperature by either conventional methods for bimolecular processes or by competitive reactions. It was found that the rate constants for conjugated olefins were larger than those for simple mono‐olefins by factors of 103–104. Temperature dependence studies reveal that the difference in the rate constants for the two types of reactions can primarily be attributed to differences in their activation energies:k1,3‐cyclohexadiene= 5.8 × 10−14exp[−(6.1 ± 1.6)/RT] cm3molecule−1s−1;kcis‐2‐butene= 4.68 × 10−14exp(−11.2/RT) cm3molecule−1s−1[2]. A linear free energy relationship between the reactions of OH and NO2with con

ISSN:0538-8066    

DOI:10.1002/kin.550180102

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractThe kinetics and mechanism of electron transfer between stable verdazyl radicals via bridge Mn(II), Co(II), Ni(II), Cu(I), and Zn ions have been studied in the range 280–330 K using the stopped‐flow technique. It was found that the kinetic features of the reactions could be described in terms of the Marcus theory. The reorganization energy of the inner coordination sphere (ICS) of intermediate complexes was estimated from the reported data on the energy of release of various ligands from the ICS of similar complexes. The rest of the kinetic parameters (solvent reorganization energy, transmission coefficients, enthalpy, and entropy of activation) were determined from Marcus equations and from plots of rate constant versus temperature, “standard” free energy, and polarity of the medium. It was also found that the reactions under consideration are nonadiabatic and the transmission coefficient value depends on the mean lifetimes of ligands in

ISSN:0538-8066    

DOI:10.1002/kin.550180103

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractHydrogen abstraction by 1‐phenylethyl radicals (ṘH) from phenylmethyl‐carbinol (HROH) and benzyl alcohol (H2R′OH) has been studied in the liquid phase at 120°C. 1‐Phenylethyl radicals have been generated by thermal decomposition ofazo‐bis‐1‐phenyl ethane and the formation of ethylbenzene (RH2), acetophenone (RO), and 2,3‐di‐phenyl butane (R2H2) has been monitored during the reaction.In order to optimize the experimental conditions, a mechanism has been assumed for the various pathways of the disappearance of ṘH and by using estimated rate parameters a presimulation was performed.The relative rate constants obtained are:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {\frac{{k_{\rm H} }}{{\sqrt {{\rm 2}k_t } }} = 1.4{\rm } \times {\rm }10^{ - 4} {\rm L}^{1/2} {\rm mol}^{ - 1/2} {\rm s}^{ - 1/2} } & {{\rm for}} & {{\rm HROH}} \\ \end{array} $$\end{document}and\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {\frac{{k_{\rm H} }}{{\sqrt {{\rm 2}k_t } }} = 1.0{\rm } \times {\rm }10^{ - 4} {\rm L}^{1/2} {\rm mol}^{ - 1/2} {\rm s}^{ - 1/2} } & {{\rm for}} & {{\rm H}_{\rm 2} {\rm R'OH}} \\ \end{array} $$\end{document}wherekHrefers to the hydrogen abstraction whilektis the combination rate coeffici

ISSN:0538-8066    

DOI:10.1002/kin.550180104

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractThe reactionwas investigated in the gas phase over the range 80–225°C using the photolysis of heptafluoroisopropyl iodide as the source of radicals. The rate constant, based on the value of 1013.36cm3mol−1s−1for the recombination ofi‐C3F7radicals, is given by\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log(}{{k_3 } \mathord{\left/ {\vphantom {{k_3 } {{\rm cm}^{\rm 3} }}} \right. \kern-\nulldelimiterspace} {{\rm cm}^{\rm 3} }}{\rm mol}^{ - 1} {\rm s}^{ - 1}) = (13.10 \pm 0.20) - {{(14000 \pm 280)} \mathord{\left/ {\vphantom {{(14000 \pm 280)} \theta }} \right. \kern-\nulldelimiterspace} \theta } $$\end{document}where θ = 2.303RT/cal mol−1. Arrhenius parameters for chlorine abstraction from CCl4by CF3, C2F5,n‐C3F7, and some hydrogenated radicals

ISSN:0538-8066    

DOI:10.1002/kin.550180105

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractThe kinetics of the oxidation of aliphatic aldehydes, formaldehyde, acetaldehyde, propionaldehyde,n‐butyraldehyde, and trichloroacetaldehyde by Peroxomonosulphate (PMS) was carried out in aqueous perchloric acid medium (0.1–1 M H+) at constant ionic strength of 1.2 M in the temperature range 10°–60°C. The reactions of all the aldehydes were found to obey a total second‐order kinetics, first order each with respect to [Peroxomonosulphate] and [aldehyde]. Acetaldehyde, propionaldehyde, andn‐butyraldehyde exhibited acid catalysis with the concurrent occurrence of acid‐independent reaction path conforming to the rate law\documentclass{article}\pagestyle{empty}\begin{document}$$ - \frac{{d[{\rm PMS]}}}{{dt}} = k_a [{\rm PMS] [aldehyde] [H}^ +] + k_b [{\rm PMS] [aldehyde]} $$\end{document}Formaldehyde was found to undergo oxidation only by acid‐dependent path (kb= 0) and trichloroacetaldehyde exhibited only the acid‐independent reaction path (ka= 0). The products of oxidation were found to be the respective carboxylic acids in each case. The stoichiometry of the reaction, [Peroxomonosulphate]:[Aldehyde]= 1:1, indicated the absence of carbonyl‐assisted decomposition and self‐decomposition of peroxomonosulphate. The kinetic and thermodynamic parameters evaluated pointed to the mechanism of a fast nucleophilic attack of the oxidant on the aldehyde followed by slow acid catalyzed and/or uncatalyzed decomposition of the intermediate to product. A sharp comparison is made with the corresponding reactions of the similar peroxide

ISSN:0538-8066    

DOI:10.1002/kin.550180106

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractThe experimental data for the reactions of oxygen atoms with methane, ethane, and neopentane at temperatures below ca. 600 K have been reexamined. In the case of CH4and C2H6reactions, detailed computer models have been assembled to test the assumptions regarding stoichiometries that were made in the original studies in order to derive elementary rate coefficients from the experimentally observed reaction rates. It was found in both cases that the measurements are especially sensitive to secondary reactions not taken into account and impurities in the reagent alkane. Because the original reports did not include sufficient experimental details, it is not now possible to correct their results quantitatively. However, it appears, qualitatively, that the values for the O + CH4and O + C2H6rate coefficients were overestimated by factors of approximately 2 to 3 in the 250–400 K temperature range, with the error increasing asTdecreases. Although the experimental results for the O + neopentane reaction are not as sensitive to the same kinds of complications, a comparison of the low‐temperature measurements with those for the O + ethane reaction suggests that the previously recommended rate coefficients, based on the data of Herron and Huie, are probably also too high by a factor of 2 t

ISSN:0538-8066    

DOI:10.1002/kin.550180107

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractWe present a kinetic study of the reactions of ground‐state sodium atoms with the molecules CH3F, CH3Cl, CH3Br, HCl, and HBr at elevated temperatures (537–966 K). Na(32S1/2) was generated by the pulsed irradiation of various sodium halide vapors and monitored by time‐resolved atomic resonance absorption of the unresolved D‐lines at λ = 589 nm [Na(32PJ) ← Na(32S1/2)] in the “single‐shot mode.” The photoelectric signals were amplified without distortion, captured, and digitized in a transient recorder interfaced to a microcomputer for data analysis. Absolute second‐order rate constants were measured at various temperatures in each case, yielding the following Arrhenius parameters (kRX=Aexp(–E/RT), errors 1σ):which constitute, to the best of our knowledge, the first direct measurements of these quantities. The reaction between Na and HBr demonstrated anomalous behaviour which is discussed in terms of potential surfaces that have been calculated previously for this type of collisional process. The data are compared with analogous results for Na + CF4, CF3Cl, and CF3Br and with single‐temperature measureme

ISSN:0538-8066    

DOI:10.1002/kin.550180108

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractConventional transition‐state theory is used for extrapolating rate coefficients for reactions of O atoms with alkanes to temperatures above the range of experimental data. Expressions are developed for estimating structural properties of the activated complex necessary for calculating enthalpies and entropies of activation. Particular attention is given to the problem of the effect of the O atom adduct on the internal rotations in the activated complex. Differences between primary, secondary, and tertiary attack are discussed, and the validity of representing the activated complexes of all O + alkane reactions by a fixed set of vibrational frequencies and other internal modes is evaluated. Experimental data for reactions of O atoms with 15 different alkanes (CH4, C2H6, C3H8, C4H10, C5H12, C6H14, C7H16, C8H18,i–C4H10, (CH3)4C, (CH3)2CHCH(CH3)2, (CH3)3CC(CH3)3,c–C5H10,c–C6H12,c–C7H14) are reviewed.The following approximate expressions for ΔS‡(298) andE(298), the entropy and energy of activation, respectively, are consistent with the experimental data and with the calculations:wherenC= number of carbon atoms in the alkane andnH= the number of “equivalent” H atoms. Using the conventional transition state theory expression,k(298) = 1015.06exp(ΔS‡/R) exp(–E(298)/298R) L mol−1s−1, one then obtains:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm log }k(298) = 5.2 + \log {\rm }{{n_{\rm H} } \mathord{\left/ {\vphantom {{n_{\rm H} } {n_{\rm C} }}} \right. \kern-\nulldelimiterspace} {n_{\rm C} }}}{{\rm (primary H, unbranched)}} \\ { = 5.7 + \log {\rm }{{n_{\rm H} } \mathord{\left/ {\vphantom {{n_{\rm H} } {n_{\rm C} }}} \right. \kern-\nulldelimiterspace} {n_{\rm C} }}}{({\rm primary H, branched)}} \\ { = 7.5 + \log {\rm }{{n_{\rm H} } \mathord{\left/ {\vphantom {{n_{\rm H} } {n_{\rm C} }}} \right. \kern-\nulldelimiterspace} {n_{\rm C} }}}{({\rm secondary H, noncyclic)}} \\ { = 8.1}{({\rm secondary H, cyclic)}} \\ { = 8.5 + \log {\rm }{{n_{\rm H} } \mathord{\left/ {\vphantom {{n_{\rm H} } {n_{\rm C} }}} \right. \kern-\nulldelimiterspace} {n_{\rm C} }}}{({\rm tertiary H)}} \\ \end{array} $$\end{document}These expressions agree with experimental values within a factor approximately 2 for

ISSN:0538-8066    

DOI:10.1002/kin.550180109

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550180101

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY