摘要:

AbstractRate coefficients for the ethoxydechlorination of 1‐chloro‐2,4‐dinitrobenzene were measured in mixtures of EtOH and EtOD of different deuterium atom fractionn(n= 0., 0.259, 0.377, 0.581, 0.767, 0.958), at 25°C. The extreme solvent isotope effect, obtained by different extrapolation procedures, is (kD/kH) = 1.90 ± 0.02. The curved variation ofkn/kHwithnis interpreted by fractionation factor theory in terms of hydrogen‐bonding solvation of ethoxide ion and transit

ISSN:0538-8066    

DOI:10.1002/kin.550050602

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe reactions of 1‐chloro‐2,3‐epoxypropane withn‐butyl and isobutyl alcohols and their 3‐chloro‐2‐hydroxypropyl ethers, respectively, in the presence of boron fluoride diethyl etherate catalyst are of the first order with regard to 1‐chloro‐2,3‐epoxypropane as well as to the catalyst. In the catalyst concentration range of 1.4 to 47.3 mmol/l., the participation of the catalyst in the reaction is incomplete. The mechanism of the reactions resembles SN2 in regard to changes of activation entropy and influence of dielectric constant of the reaction medium upon the reaction rate. The established values ofK(the ratio of propagation to initiation rates) are suitable for calculating the compositions of the adducts obtained. The experimentally obtained yields of 3‐chloro‐2‐hydroxypropyl ethers of lower alcohols are compared with those calculated from the kinetica

ISSN:0538-8066    

DOI:10.1002/kin.550050603

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

Abstract2,4‐Dimethylhexene‐l has been decomposed in single‐pulse shock tube experiments. Rate expressions for the initial reactions are\documentclass{article}\pagestyle{empty}\begin{document}$$ k(C_4 H_7 - S - C_4 H_9 \to C_4 H_7 .(isobutenyl) + s - C_4 H_9 .) = 10^{15.6} \exp (- 33,200/T)\sec ^{ - 1} $$\end{document}and\documentclass{article}\pagestyle{empty}\begin{document}$$ k(C_4 H_7 - S - C_4 H_8 \to _i C_4 H_8 + n - C_4 H_8 .) = 10^{12.5} \exp (- 26,900/T)\sec ^{ - 1} $$\end{document}sec−1at 1.5–5 atm and 1050°K. This leads to ΔH°f300(CH2= C(CH3)CH2) = 124 kJ/mol, or an allylic resonance energy of 50 kJ/mol. Rate expressions for the decomposition of the appropriate olefins which yield isobutenyl radicals and methyl, ethyl, isopropyl,n‐propyl,t‐butyl, andt‐amyl radicals, respectively, are presented. The rate expression for the decomposition of isobutenyl radical is\documentclass{article}\pagestyle{empty}\begin{document}$$ k{\rm (C}_{\rm 4} H_7 .(isobutenyl) \to C_3 H_4 (allene) + CH_3 .) = 10^{13.3} \exp (- 2,500/T)\sec ^{ - 1} $$\end{document}(at the beginning of the fall‐off region). For the combination of isobutenyl and methyl radicals, the rate constant at 1020°K is\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm k(C}_{\rm 4} H_7 .(isobutenyl) + CH_3 . \to 2 - methylbutene - 1) = 10^{10.3} 1./mol\sec $$\end{document}Combination of this number and the calculated rate expression for 2‐methylbutene‐1 decomposition givesS C 4H 7. (1100) = 470 J/mol °K. This yields\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm k(C}H_3 + C_3 H_4 (allene) \to C_4 H_7 .(isobutenyl) = 10^{8.2} \exp (- 2,500/T)l./mol\sec $$\end{document}It is demonstrated that an upper limit for the rate of hydrogen abstraction by isobutenyl from toluene is\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm k(C}_{\rm 4} H_7 . + \emptyset CH_3 \to iC_4 H_8 + \emptyset CH_2 .)\underline \le 10^{8.3} \exp (- 6,

ISSN:0538-8066    

DOI:10.1002/kin.550050604

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe experimental results on decomposition and combination reactions involving O3, HNO3, NH3, C2N2, and NO2Cl over extended temperature and pressure ranges are compared with the deductions from RRKM calculations. Quantitative fits of the data over the entire range are possible only if the external (overall) rotations are assumed to be involved in the reactions. Recommended rate constants for the reactions O + O2+ N2→ O3+ N2and OH + NO2+ N2→ HNO3+ N2are presen

ISSN:0538-8066    

DOI:10.1002/kin.550050605

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe thermal, unimolecular elimination of HF from CH3CF3was studied by three different groups over the temperature range 1000° to 1800°K. While the reported kinetic parameters varied greatly, it is shown here that these data may be satisfactorily correlated in terms of a four‐center transition state. This correlation results in ΔE 00 ++= 69.2 kcal/mol, and log (k/s−1) = 14.6 – 72.6/θ. These results may then be combined with the kinetics of the chemically activated elimination of HF from CH3CF3formed by the recombination of methyl and trifluoromethyl radicals. The data from three different laboratories are shown to be in excellent agreement. These data, combined with extant thermal data, yield as a best valueDH 00(CH3CF3) = 99.6 ± 1.1 kcal/mol. This gives the unexpectedly high value of DH298°(CH3CF3) = 101.2 ± 1.1 kcal/mol. It is suggested that dipoledipole interactions, primarily in CH3CF3, account for this surprisingly strong CC bond dissociation energy. These results also yield δH f0(CH3CF3; g, 2

ISSN:0538-8066    

DOI:10.1002/kin.550050606

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractCompeting first‐ and second‐order reactions of transient molecular species (e.g., triplet states and free radicals) are a common occurrence in kinetic studies such as flash photolysis and pulse radiolysis. We have developed a method for analyzing the decay kinetics of any species (Y) whose disappearance is described by −dY/dt=k1Y+k2Y2. The computer program (written in time‐sharing BASIC) employs an iterative technique to obtain the least‐squares estimates of the three parameters in the integrated rate

ISSN:0538-8066    

DOI:10.1002/kin.550050607

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractPyrolysis ofcis‐butene‐2 under conditions of very low pressure (VLPP) has been studied in the range of 1100–1300°K. The principal products are butadiene and H2, obtained in a unimolecular reaction. A competing reaction to form butene‐l accounts for from 10% to 40% of the overall decomposition over the range. Using a «tight» model for the transition state and RRKM theory yields a high‐pressure, unimolecular rate constant for the 1,4‐H2elimination of\documentclass{article}\pagestyle{empty}\begin{document}$$ \log \,k\left( {{\rm s}^{ - 1} } \right) = \left( {13.0 \pm 0.6} \right) - {{\left( {65 \pm 2} \right)} \mathord{\left/ {\vphantom {{\left( {65 \pm 2} \right)} \theta }} \right. \kern-\nulldelimiterspace} \theta } $$\end{document}where θ = 2.303RTin kcal/mol. There is some surface reaction of butadiene at these temperatures to yield H2+ nonvolatile residue. Butene‐l proceeds to decompose irreversibly to allyl + methyl radicals which have been observed directly. Comparison with related reactions leads to the conclusion that orbital symmetry‐forbidden, 1,2‐H2elimination from saturated organic compounds will have activation energie

ISSN:0538-8066    

DOI:10.1002/kin.550050608

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe kinetics of the gas‐phase reaction of 2,2,2‐trifluoroethyl iodide with hydrogen iodide has been studied over the temperature range of 525°K to 602°K and a tenfold variation in the ratio of CF3CH2I/HI. The experimental results are in good agreement with the expected free radical‐mechanism:\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm I}_2 + {\rm M} \rightleftharpoons 2{\rm I} + {\rm M} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm RI} + {\rm I}\mathop{\rightleftharpoons}\limits_2^1 {\rm R} + {\rm I}_2 $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm R} + {\rm HI} \mathop{\rightleftharpoons} \limits_{4}^{3} {\rm RH} + {\rm I} $$\end{document}An analysis of the kinetic data yield:\documentclass{article}\pagestyle{empty}\begin{document}$$ \log (k_1/ \rm I. \rm mol^{ - 1} s^{ - 1}) = (11.5 \pm 0.1) - (1.99 \pm 0.2)/\theta $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_2 /k_3 = (0.65 \pm 0.4) + 1.0/\theta $$\end{document}where θ =2.303RTin kcal/mol. If these results are combined with the assumption thatE2= 0 ± 1 kcal/mol, then one obtainsDH 0298(CF3CH2I) = 56.3 kcal/mol. This result may be compared withDH 0298(CH3CH2I) = 52.9 kcal/mol and suggests that substitution of three fluorines for hydrogen in the beta position strengthens the

ISSN:0538-8066    

DOI:10.1002/kin.550050609

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe pyrolysis of isobutane was investigated in the ranges of 770° to 855°K and 20 to 150 Torr at up to 4% decomposition. The reaction is homogeneous and strongly self‐inhibited. A simple Rice‐Herzfeld chain terminated by the recombination of methyl radicals is proposed for the initial, uninhibited reaction. Self‐inhibition is due to abstraction of hydrogen atoms from product isobutene giving resonance‐stabilized 2‐methylallyl radicals which participate in termination reactions. The reaction chains are shown to be long. It is suggested that a previously published rate constant for the initiation reaction (1)\documentclass{article}\pagestyle{empty}\begin{document}$$ i - C_4 H_{10} \to CH_3 + i - C_3 H_7 $$\end{document}is incorrect and the valuek1= 1016.8exp (−81700 cal mol−1/RT)s−1is recommended. The values of the rate constants for the reactions (4i)\documentclass{article}\pagestyle{empty}\begin{document}$$ CH_3 + i - C_4 H_{10} \to CH_3 + i - C_4 H_9 $$\end{document}(4t)\documentclass{article}\pagestyle{empty}\begin{document}$$ CH_3 + i - C_4 H_{10} \to CH_4 + t - C_4 H_9 $$\end{document}(8)\documentclass{article}\pagestyle{empty}\begin{document}$$ CH_3 + i - C_4 H_8 \to CH_4 + 2 - methylallyl $$\end{document}are estimated to be\documentclass{article}\pagestyle{empty}\begin{document}$$ k_{4i} = 10^{13.16} \exp (- 16300calmol^{ - 1} /RT)cm^3 mol^{ - 1} s^{ - 1} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ k_{4t} = 10^{12.51} \exp (- 12900calmol^{ - 1} /RT)cm^3 mol^{ - 1} s^{ - 1} $$\end{document}and\documentclass{article}\pagestyle{empty}\begin{document}$$ k_{8} = 10^{14.05} \exp (- 17600calmol^{ - 1} /RT)cm^3 mol^{ - 1} s^{ - 1} $$\end{document}From a recalculation of previously published data on the pyrolysis of isobutane at lower temperatures and higher pressures, the valuek11c, = 109.6cm3mol−1s−1is obtained for the rate constant of recombination oft‐butyl. A calculation which is independent of any assumed rate constants or thermochemistry shows that the predominant chain termination reaction is the recombination of two methyl radicals in the conditions of the present work and the recombination of twot‐butyl radicals in those of our previous study at lower temperat

ISSN:0538-8066    

DOI:10.1002/kin.550050610

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractRate constants for the low‐pressure unimolecular decomposition of ONBr and ONCl in an argon bath have been determined at temperatures in the vicinity of 1000°K. Both molecules exhibit the usual depression of the observed activation energy below the bond dissociation energy. The Arrhenius expressions obtained are (units of cc mole−1sec−1):\documentclass{article}\pagestyle{empty}\begin{document}$$ ONBr - Ar:\log k = (15.06 \pm 0.27) - (25.06 \pm 1.13)kcalmole^{ - 1} /\theta $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ ONCl - Ar:\log k = (15.95 \pm 0.52) - (43.79 \pm 2.04)kcalmole^{ - 1} /\theta $$\end{document}Treatment of the data by the classical RRK theory yieldss≅ 2.7 ± 1 for ONCl and 3.0 ± 0.6 for ONBr. Coupling the shock tube results for ONCl with lower‐temperature data from Ashmore and Burnett [3], one obtainss≅ 2.5 ± 0.5 and λ ≈︁ 1. If it is assumed thatsis also 2.5 for ONBr, then one finds the surprising (but tentative) result that λONCl

ISSN:0538-8066    

DOI:10.1002/kin.550050611

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY