摘要:

AbstractThe kinetics of the reaction between CH3and HCl was studied in a tubular reactor coupled to a photoionization mass spectrometer. Rate constants were measured as a function of temperature (296–495 K) and were fitted to an Arrhenius expression:k1= 5.0(±0.7) × 10−13exp{−1.4(±0.3) kcal mol−1/RT} cm3molecule−1s−1. This information was combined with known kinetic parameters of the reverse reaction to obtain Second Law determinations of the methyl radical heat of formation {34.7(±0.6) kcal mol−1} and entropy {46(±2) cal mol−1K−1} at 298 K. Using the known entropy of CH3, a more accurate Third Law determination of the CH3heat of formation at this temperature was also obtained {34.8(±0.3) kcal mol−1}. The values ofk1obtained in this study are between those reported in prior investigations. The results were also used to test the accuracy of the thermochemical information which can be obtained from kinetic studies of R + HX (X = Cl, Br, I) reactions o

ISSN:0538-8066    

DOI:10.1002/kin.550201002

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractIn order to bring more information on the thermodynamic and kinetic behavior of nitryl chloride in aprotic media, we have surveyed exhaustively the first NO2Cl‐reduction step in sulfolane (at the platinum electrode), taking into account our preliminary results about the electrochemical properties of NO2Cl in aprotic solvents. We have excluded the intervention of the weak ionic dissociation of NO2Cl (NO2Cl ⇆ NO 2++ Cl−[I]) and its slow molecular decomposition as: 2NO2Cl ⇄ Cl2+ 2NO 2•(⇄ N2O4) [II] in this process. We have admitted the occurrence of a rapid chemical reaction which controls kinetically the electrochemical system studied:\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm NO} + {\rm NO}_{\rm 2} {\rm Cl}\buildrel {k^*} \over \longrightarrow {\rm NOCl} + {\rm NO}_{\rm 2}^ \cdot {\rm}[{\rm III]} $\end{document}. By analyzing the kinetic currents resulting from the 1 st cathodic wave of NO2Cl at the temperature range 303–323 K, the rate constant,k*, and the activation energy,E*, of reaction [III] have been determined. These results and those previously found in the gas ph

ISSN:0538-8066    

DOI:10.1002/kin.550201003

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractRate constants for the unimolecular dissociation of 1,3‐butadiene have been measured with the pulsed laser flash absorption technique, following butadiene disappearance at 222 nm. The results are in excellent agreement with previous laser‐schlieren measurements interpreted with a ΔH°298= 100 kcal/mol heat of dissociation. A new RRKM calculation agreeing with both sets of rate constants gives logk∞(s−1) = 17.03 ± 0.3 – 94(kcal/mol)/RT. These data and product measurements using ARAS, single‐pulse product analysis, and time‐of‐flight mass spectrometry, in shock tubes, all provide independent evidence against any major participation by molecular reactions in the dissociation. The only dissociation channel, or combination of channels, consistent with all the measurements is C‐C scission to two vinyl radicals. However, the extremely slow rate of H‐atom formation seen in ARAS experiments then requires an unacceptably low rate

ISSN:0538-8066    

DOI:10.1002/kin.550201004

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe third order rate coefficients for the addition reaction of Cl with NO2, Cl + NO2+ M → ClNO2(ClONO) + M;k1, were measured to bek1(He) = (7.5 ± 1.1) × 10−31cm6molecule−2s−1andk1(N2) = (16.6 ± 3.0) × 10−31cm6molecule−2s−1at 298 K using the flash photolysis‐resonance fluorescence method. The pressure range of the study was 15 to 500 torr He and 19 to 200 torr N2. The temperature dependence of the third order rate coefficients were also measured between 240 and 350 K. The 298 K results are compared with those from previous l

ISSN:0538-8066    

DOI:10.1002/kin.550201005

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe ultraviolet absorption spectra of chloromethylperoxy and fluoromethylperoxy radicals, CH2ClO2and CH2FO2, and the kinetics of their respective self reactions have been studied in the gas phase using a flash photolysis technique. The absorption spectra for both radicals were quantified over the wavelength range 210 and 290 nm. The measured absorption cross‐sections\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} \sigma _{{\rm CH}_{\rm 2} {\rm ClO}_{\rm 2}} (250{\rm nm)} = (3.14 \pm 0.45) \times 10^{- 18} {\rm cm}^{\rm 2} {\rm molecule}^{- 1} \\ \sigma _{{\rm CH}_{\rm 2} {\rm FO}_{\rm 2}} (240{\rm nm)} = (3.72 \pm 0.45) \times 10^{- 18} {\rm cm}^{\rm 2} {\rm molecule}^{- 1} \\ \end{array} $$\end{document}were used to derive the observed self‐reaction rate constants (for reactions 1 and 2) over the temperature range 228–380 K, defined as –d[CH2XO2]/dt = 2k[CH2XO2]2, whereXrepresents Cl or F.The rate constants at 298 K were found to be independent of pressure over the range 25–400 torr N2with values ofk1(298 K) = (3.78 ± 0.45) × 10−12andk2(298 K) = (3.07 ± 0.65) × 10−12in units of cm3molecule−1s−1. The kinetic data over the complete temperature range are represented by the Arrhenius expressions:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} k_1 = (3.1 \pm 1.1) \times 10^{- 13} \exp [(735 \pm 95)/{\rm T] cm}^{\rm 3} {\rm molecule}^{- 1} {\rm s}^{- 1} \\ k_2 = (3.3 \pm 1.2) \times 10^{- 13} \exp [(700 \pm 100)/{\rm T] cm}^{\rm 3} {\rm molecule}^{- 1} {\rm s}^{- 1} \\\end{array} $$\end{document}where the error limits represent 2σ from linear least squares analysis. These results are discussed with respect to previous measurements of the absorption spectra and reactions o

ISSN:0538-8066    

DOI:10.1002/kin.550201006

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550201007

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550201001

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY