摘要:

AbstractRate constants for the combination of methyl radicals with NO and O2have been measured by flash photolysis of azomethane coupled with product analysis by gas chromatography. Values of the rate constants have been obtained over the pressure region from 50 to 700 torr with He, N2, and Ar as quenching molecules.The high‐pressure limits were obtained through an RRKM model calculation and were found to be\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm CH}_{\rm 3} + {\rm NO} + {\rm M} \to {\rm CH}_{\rm 3} {\rm NO} + {\rm M}} \hfill & {k_\infty = 3.2 \times 10^{ - 11} {{{\rm cm}^{\rm 3} } \mathord{\left/ {\vphantom {{{\rm cm}^{\rm 3} } {{\rm molec} \cdot {\rm sec}}}} \right. \kern-\nulldelimiterspace} {{\rm molec} \cdot {\rm sec}}}} \hfill \\ {{\rm CH}_{\rm 3} + {\rm O}_{\rm 2} + {\rm M} \to {\rm CH}_{\rm 3} {\rm O}_{\rm 2} + {\rm M}} \hfill & {k_\infty = 1.7 \times 10^{ - 12} {{{\rm cm}^{\rm 3} } \mathord{\left/ {\vphantom {{{\rm cm}^{\rm 3} } {{\rm molec} \cdot {\rm sec}}}} \right. \kern-\nulldelimiterspace} {{\rm molec} \cdot {\rm sec}}}} \hfill \\ \end{array} $$\end{document}The rate constants were measured relative to the methyl combination reactionk1withk1= 9.5 × 10−11cm3/molec · sec. The RRKM model suggests D0(CH3O2) = 32 ± 3 k

ISSN:0538-8066    

DOI:10.1002/kin.550070502

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractA semiempirical approach has been used to evaluate rate parameters for a three‐center decomposition reaction from the point of view of transition state theory, with perfluorodiazirine serving as the prototype molecule. Several activated complex models are considered in which the reaction coordinate is chosen as the ∡ NCN bending mode. The constraints imposed include the principle of concerted bond‐order conservation in passing from the initial to the final state, and use is made of empirical bond order–bond length and bond order–force constant relationships. The geometric configuration of the transition state sought is one which conforms with the lowest energy path and is also consistent with the observed entropy of activation. The potential energy of activation is taken as the optimum difference in binding energies (based on the INDO method) between the transition and initial states, and the critical energy is obtained by applying a correction for the zero‐point energy difference, derived from normal coordinate analysis. Satisfactory agreement is found in the case of the activated complex model for which the total bond order is conserved and bonds undergoing rupture are assigned a fractional bond order (FBO) of 2/3, derived from the postulate (FBO) = α/β whe re α(=2) is the number of bonds breaking, and β(=3) is the number of bonds undergoing change in t

ISSN:0538-8066    

DOI:10.1002/kin.550070503

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe oxidation of acetylene by water vapor was studied behind the reflected shock in a single‐pulse shock tube. Computer simulation experiments reproduced the experimental results in the temperature range of 1500 to 2000°K. The kinetic scheme suggested here involves three major processes, (1) production of hydrogen atoms by the sequence of reactions which lead from acetylene to carbon; (2) production of OH radicals, mainly by the reaction H + H2O → H2+ OH, and (3) fast oxidation of the acetylene and other C/H species by the available oxidants in the system. The experimental results of methane oxidation suggest that methane is converted to acetylene prior to its oxidation. The implication of the experimental results to processes occurring in planetary atmospheres as a result of thunder shock waves is briefly discu

ISSN:0538-8066    

DOI:10.1002/kin.550070504

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe pyrolysis of tetrafluorohydrazine has been studied from 578 to 791°K. The stoichiometry has been established as\documentclass{article}\pagestyle{empty}\begin{document}$$ 6{\rm NF}_{\rm 2} \to 4{\rm NF}_{\rm 3} + {\rm N}_{\rm 2} $$\end{document}Reaction rates have been measured and the effects of surface area, inert gas pressure, and nitric oxide have been examined. The rate‐determining step proposed is\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm 2NF}_{\rm 2} \to {\rm NF}_{\rm 3} + {\rm NF} $$\end{document}and the general rate expression obtained for this is\documentclass{article}\pagestyle{empty}\begin{document}$$ k_1 = 10^{9.0 \pm 0.4} \exp {{ - 36,950 \pm 500} \mathord{\left/ {\vphantom {{ - 36,950 \pm 500} {RTM^{ - 1} \cdot \sec ^{ - 1} }}} \right. \kern-\nulldelimiterspace} {RTM^{ - 1} \cdot \sec ^{ - 1} }} $$\end{docume

ISSN:0538-8066    

DOI:10.1002/kin.550070505

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe absolute rate constant of the reaction of O(3P) with toluene was measured by the microwave discharge‐fast‐flow method to obtainkT= 109.7–2.7/2.303RTl./mole·sec at 100–375°C. This was in good agreement with the rate constant calculated from the combination of the relative rate constant obtained by Jones and Cvetanovic with the recently determined absolute rate constants of the reaction of O(3P) + olefins. The extrapolation of the above Arrhenius plot to 27°C was also in good agreement with the absolute value ofkT= 4.5 × 107l./mole·sec determined recently by Atkinson and Pitts at 27°C. The rate constant of the reaction of chlorobenzene with O(3P), obtained at 238°C as 108.3l./mole·sec by a competitive method, was smaller thankTby a factor of about two at the s

ISSN:0538-8066    

DOI:10.1002/kin.550070506

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe kinetics of the radiation‐induced free radical chain reactions in solutions of CCl3CClH2and CCl2BrCH2Cl in cyclohexane (RH) were studied in the temperature range of 90–225°C. 1,1,2 trichloroethyl and 1,1,1,2 tetrachloroethyl radicals were produced by the reaction of radiolytically generated cyclohexyl (R) radicals with solutes. The reactions studied wereThe following rate expressins were obtained:\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log}\left({{{k_2 } \mathord{\left/ {\vphantom {{k_2 } {k_3 }}} \right.\kern-\nulldelimiterspace} {k_3 }}} \right) = 1.37 \pm 0.24 + {{\left({0.47 \pm 0.48} \right)} \mathord{\left/ {\vphantom {{\left({0.47 \pm 0.48} \right)} \theta }} \right. \kern-\nulldelimiterspace} \theta } $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log}\left({{{k_5 } \mathord{\left/ {\vphantom {{k_5 } {k_4 }}} \right.\kern-\nulldelimiterspace} {k_4 }}} \right)\left({{{{\rm mole}} \mathord{\left/{\vphantom {{{\rm mole}} {l.}}} \right.\kern-\nulldelimiterspace} {l.}}} \right) = \left({5.49 \pm 0.09} \right) - {{\left({9.47 \pm 0.18} \right)} \mathord{\left/{\vphantom {{\left({9.47 \pm 0.18} \right)} \theta }} \right.\kern-\nulldelimiterspace} \theta } $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log}\left({{{k_{14} } \mathord{\left/ {\vphantom {{k_{14} } {k_{13} }}} \right. \kern-\nulldelimiterspace} {k_{13} }}} \right) = \left({0.57 \pm 0.56} \right) - {{\left({6.71 \pm 1.15} \right)} \mathord{\left/ {\vphantom {{\left({6.71 \pm 1.15} \right)} \theta }} \right. \kern-\nulldelimiterspace} \theta } $$\end{document}where θ = 2.303RTin kcal/mole. From the activation parameters of thek4/k5rate constant ratio and the assumption thatE4=E CCl 3+RH,E5was calculated to be 20.2 ± 0.2 kcal/mole. The Arrhenius parameters for the Cl atom elimination reaction from chloroethyl radicals derived from liquid and gas‐phase studies

ISSN:0538-8066    

DOI:10.1002/kin.550070507

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe high‐pressure absolute rate constants for the decomposition of nitrosobenzene and pentafluoronitrosobenzene were determined using the very‐low‐pressure pyrolysis (VLPP) technique.Bond dissociation energies of DH0(C6H5NO) = 51.5 ± 1 kcal/mole and DH0(C6F5NO) = 50.5 ± 1 kcal/mole could be deduced if the radical combination rate constant is set at logkr(M−1·sec−1) = 10.0 ± 0.5 for both systems and the activation energy for combination is taken as 0 kcal/mole at 298°K. δHf0(C6H5NO), δHf0(C6F5NO), and δHf0(C6F5) could be estimated from our kinetic data and group additivity. The values are 48.1 ± 1, –160 ± 2, and – 130.9 ± 2 kcal/mole, respectively. C–X bond dissociation energies of several perfluorinated phenyl compounds, DH0(C6F5–X), were obtained from the reported values of δHf0(C6F5X) and our estimated δHf0(C6F5) [X =

ISSN:0538-8066    

DOI:10.1002/kin.550070508

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe pyrolysis ofn‐propyl nitrate andtert‐butyl nitrite at very low pressures (VLPP technique) is reported. For the reaction the high‐pressure rate expression at 300°K, logk1(sec−1) = 16.5 − 40.0 kcal/mole/2.3RT, is derived. The reaction was studied and the high‐pressure parameters at 300°K are logk2(sec−1) = 15.8 − 39.3 kcal/mole/2.3RT. From ΔS1,−10and ΔS2,−20and the assumptionE−1andE−2⋍ 0, we derive logk−1(M−1·sec−1) (300°K) = 9.5 and logk−2(M−1·sec−1) (300°K) = 9.8. In contrast, the pyrolysis of methyl nitrite and methyl d3nitrite afford NO and HNO and DNO, respectively, in what appears to be a heterogeneous process. The values ofk−1andk−2in conjunction with independent measurements imply a value at 300°K for of 3.5 × 105M−1·sec−1, which is two orders of magnitude greater than currently accepted values.In the high‐pressure static pyrolysis of dimethyl peroxide in the presence of NO2, the yield of methyl nitrate indicates that the combination of methoxy radicals wit

ISSN:0538-8066    

DOI:10.1002/kin.550070509

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe photolysis ofcis‐1,2‐dichloroethylene has been investigated in the presence of I2as a function of incident wavelength and as a function of initialcispressure. The results indicate that at ±>2200Å the following primary processes occur:\documentclass{article}\pagestyle{empty}\begin{document}$$ cis{\rm - 1,}2{\rm - C}_{\rm 2} {\rm H}_{\rm 2} {\rm Cl}_{\rm 2}^ * \to {\rm C}_{\rm 2} {\rm H}_{\rm 2} + {\rm Cl}_{\rm 2} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ cis{\rm - 1,2 - C}_{\rm 2} {\rm H}_{\rm 2} {\rm Cl}_{\rm 2}^ * \to {\rm C}_{\rm 2} {\rm HCl} + {\rm HCl} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ cis{\rm - 1,}2{\rm - C}_{\rm 2} {\rm H}_{\rm 2} {\rm Cl}_{\rm 2}^ * \to {\rm C}_{\rm 2} {\rm H}_{\rm 2} {\rm Cl} + {\rm Cl} $$\end{document}The lifetime of the excited state yielding the above products is estimated at about 2.4×10−9sec. At shorter wavelengths additional C2H2is produced by decomposition of a vibrationally excited C2H2Cl radical.Scavenging of the CHClCH radical by I2producedtransandcis‐CHClCHl in a ratio of 4 to 1, re

ISSN:0538-8066    

DOI:10.1002/kin.550070510

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe ignition of COS + O2mixtures diluted in argon was studied behind reflected shocks in a single‐pulse shock tube over the temperature range of 1100–1700°K. Ignition delay times and the distribution of reaction products before and after ignition were determined experimentally. From a total of 63 tests run at varying initial conditions, the following correlation for the induction times was derived:\documentclass{article}\pagestyle{empty}\begin{document}$$ t_{ig} = 2.66 \times 10^{ - 11} \exp \left({{E \mathord{\left/{\vphantom {E {RT}}} \right.\kern-\nulldelimiterspace} {RT}}} \right)\left[{{\rm COS}} \right]^{\beta _1 } \left[{{\rm O}_{\rm 2} } \right]^{\beta _2 } \sec . $$\end{document}where β1= +0.30, β2= 1.12, andE= 16.9 kcal/mole. Using a reaction scheme of 14 steps, the following values were obtained by a computer modeling of the induction times: β1= +0.22, β2= 1.55, andE= 17.3 kcal/mole. The calculations showed that the reaction COS + S → CO + S2caused the inhibiting effect of the COS. The reaction COS → O ± CO2+ S has a very strong accelerating effect, whereas the parallel channel COS + O → CO + SO shows the opposite effect. It was also shown that the reaction O + S2→ SO + O is very slow and does not contribute to the overall oxidation reaction. It is suggested that the rate constant given to the four‐center reaction COS + SO → CO2+ S2, that is, 1011cm3/mole · sec at 300°K is incorrect. This constant is not much higher than 108c

ISSN:0538-8066    

DOI:10.1002/kin.550070511

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY