摘要:

AbstractEthyl 4‐chlorobutyrate, which is reexamined, pyrolyzes at 350–410°C to ethylene, butyrolactone, and HCl. Under the reaction conditions, the primary product 4‐chlorobutyric acid is responsible for the formation of γ‐butyrolactone and HCl. In seasoned vessels, and in the presence of a free‐radical inhibitor, the ester elimination is homogeneous, unimolecular, and follows a first‐order rate law. For initial pressures from 69–147 Torr, the rate is given by the following Arrhenius expression: logk1(s−1) = (12.21 ± 0.26) − (197.6 ± 3.3) kJ mol−1(2.303RT)−1. The rates and product formation differ from the previous work on the chloroester pyrolysis.4‐Chlorobutyric acid, an intermediate product of the above substrate, was also pyrolyzed at 279–330°C with initial pressure within the range of 78–187 Torr. This reaction, which yields γ‐butyrolactone and HCl, is also homogeneous, unimolecular, and obeys a first‐order rate law. The rate coefficient, is given by the following Arrhenius equation: logk1(s−1) = (12.28 ± 0.41) − (172.0 ± 4.6) kJ mol−1(2.303RT)−1. The pyrolysis of ethyl chlorobutyrate proceeds by the normal mechanism of ester elimination. However, the intermediate 4‐chlorobutyric acid was found to yield butyrolactone through anchimeric assistance of the COOH group and by an intimate ion pair‐type of mechanism. Additional evidence of cyclic product and neighbo

ISSN:0538-8066    

DOI:10.1002/kin.550190902

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractA previous technique for the calculation of rate constants for the gas‐phase reactions of the OH radical with organic compounds has been updated and extended to include sulfur‐ and nitrogen‐containing compounds. The overall OH radical reaction rate constants are separated into individual processes involving (a) H‐atom abstraction from CH and OH bonds in saturated organics, (b) OH radical addition to>CCN, SH, and S groups. During its development, this estimation technique has been tested against the available database, and only for 18 out of a total of ca. 300 organic compounds do the calculated and experimental room temperature rate constants disagree by more than a factor of 2. This suggests that this technique has utility in estimating OH radical reaction rate constants at room temperature and atmospheric pressure of air, and hence atmospheric lifetimes due to OH radical reaction, for organic compounds for which experimental data are not available. In addition, OH radical reaction rate constants can be estimated over the temperature range ca. 250–1000 K for those organic compounds which react via H‐atom abstraction from CH and OH bonds, and over the temperature range ca. 250–500 K fo

ISSN:0538-8066    

DOI:10.1002/kin.550190903

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550190904

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractIn order to appreciate the excellent catalytic effect of iodine on the alcoholyses of alkoxysilanes more precisely, the rates of the reaction, Et3SiOBun+ BusOH ⇌ Et3SiOBus+ BunOH, were determined at various iodine concentrations.Both forward and reverse reactions are first order with respect to butoxysilane and to butanol, and pseudo first‐order rate constants were measured at 40°, 30°, and 20°C on reaction mixtures containing both butanols in excess by means of gas‐liquid chromatography. The observed rate constants as a function of iodine concentration gave linear relationships, and from these data the catalytic coefficients of iodine were evaluated:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {k_{2_{{\rm I}_2 } } = 7.4 \times 10^7 \exp (- 55.7 \times 10^3 /RT)} & {({\rm forward\, reaction})} \\ \end{array} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {k_{{ -2} _{{\rm I} _2 } } = 9.7 \times 10^7 \exp (- 54.3 \times 10^3 /RT)} & {({\rm reverse\, reaction})} \\ \end{array} $$\end{document}The enthalpies and the entropies of activation were estimated to be 53.2 kJ mol−1, −103 J K−1mol−1(forward, 30°C) and 51.8 kJ mol−1, minus;100 J K−

ISSN:0538-8066    

DOI:10.1002/kin.550190905

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractValues for 〈ΔEdown〉, the average downward energy transferred from the reactant to the bath gas upon collision, have been obtained for highly vibrationally excited undeuterated and per‐deuterated isopropyl bromide with the bath gases Ne, Xe, C2H4, and C2D4, at ca. 870 K. The technique of pressure‐dependent very low‐pressure pyrolysis (VLPP) was used to obtain the data. For C3H7Br, the 〈ΔEdown〉 values (cm−1) are 490 (Ne), 540 (Xe), 820 (C2H4), and 740 (C2D4), and for C3D7Br, 440 (Ne), 570 (Xe), 730 (C2H4), and 810 (C2D4). The uncertainties in these values are ca. ±10%. The 〈ΔEdown〉 values for the inert bath gases Ne and Xe show excellent agreement with the theoretical predictions of the semi‐empirical biased random walk model for monatomic/substrate collisional energy exchange [J. Chem. Phys.,80, 5501 (1984)]. The relative effects of deuteration of the reactant molecule on 〈ΔEdown〉 also compare favorably with the predictions of this theoretical model. Extrapolated high‐pressure rate coefficients (s−1) for the thermal decomposition of reactant are 1013.6±0.3exp(−200 ± 8 kJ mol−1/RT) for C3H7Br and 1013.9±0.3exp(−207 ± 8 kJ mol±1/RT) for C3D7Br, which are consistent with pre

ISSN:0538-8066    

DOI:10.1002/kin.550190906

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractA one‐parameter analytical potential energy function for β‐bonds in free radicals is described, which accounts quantitatively for their observed stretching frequencies and the position and size of the activation barriers for their fission. It is shown that such a function can be used to characterizea priorithe corresponding transition states by assuming that the structural and spectroscopic changes taking place along the minimum energy path track the development of pi bonding rather than following a simple exponential dependence on the reaction coordinate. This procedure, tested by comparing predictedA‐factors and isotope effects with experimental data for alkyl radicals andab‐initiocalculations on C2H5, fully encodes the basic features of radical decomposition reactions and provides a simple, realistic, and self‐consistent technique for the estimation of their kinetic

ISSN:0538-8066    

DOI:10.1002/kin.550190907

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550190901

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY