摘要:

AbstractThe photooxidation of the 1,3‐butadiene–NO–air system at 298 ± 2 K was investigated in an environmental chamber under simulated atmospheric conditions. The irradiation gave rise to the formation of acrolein in a 55% yield, based on 1,3‐butadiene initial concentration for all the experimental runs.The rate of formation of acrolein was the same as that of 1,3‐butadiene consumption, indicating that acrolein is the major product of the 1,3‐butadiene oxidation in air.The dependence of acrolein concentration on irradiation time showed thata secondary process, identified as an oxidation of acrolein by⋅OH radicals, was occurring during the photochemical runs. The rate constant of this secondary process was determined by measuring the relative rates of disappearance of acrolein andn‐butane during the irradiation of acrolein‐n‐butane‐NO‐air mixtures. The so obtained relative rate constant value was placed on an absolute basis using a reported rate constant for then‐butane +⋅OH reaction; a value of (1.6 ± 0.

ISSN:0538-8066    

DOI:10.1002/kin.550121202

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe rate constant for the reaction Cl + CHClO → HCl + CClO was determined from relative decay rates of CHClO and CH3Cl inthe photolysis of mixtures containing Cl2(∼1 torr), CH3Cl (∼1 torr), and O2(∼0.1 torr) in 700 torr N2. In such mixtures CHClO was generatedin situas a principal product prior to complete consumption of O2. The value ofk(Cl + CHClO)/k(Cl + CH3Cl) = 1.6 ± 0.2(3σ) combined with the literature value ofk(Cl + CH3Cl) = 4.9 × 10−13cm3/molecule sec givesk(Cl + CHClO) = 7.8 × 10−13cm3/molecule sec at 298 ± 2 K, in excellent agreement with a previous value of (7.9 ± 1.5) × 10−13cm3/molecule sec determined by Sanhueza and Heicklen [J. Phys. Chem.,79, 7 (1975)]. Thus this reaction is approximately 100 times slower than the corresponding reactions of aldehydes and alkanes with comparable CH bond e

ISSN:0538-8066    

DOI:10.1002/kin.550121203

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractH2S increases the thermal isomerization of butene‐2cis(Bc) to butene‐1 (B1) and butene‐2trans(Bt) around 500°C. This effect is interpreted on the basis of a free radical mechanism in which buten‐2‐yl and thiyl free radicals are the main chain carriers. B1formation is essentially explainedby the metathetical steps:whereas the free radical part of Btformation results from the addition–elimination processes:. It is shown that the initiation step of pure Bcthermal reaction is essentially unimolecular:and that a new initiation step occurs in the presence of H2S:. The rate constant ratio has been evaluated:\documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{k_2 }}{{k_3 }} \simeq 0.4\exp ^{ - (6500 \pm 1000)/RT} (RT\,in\,cal/mol) $$\end{document}and the best values ofk1andk1', consistent with this work and with thermochemical data, are\documentclass{article}\pagestyle{empty}\begin{document}$$ k_1 \simeq 10^{15.5 - 85,500/2.3RT} \sec ^{ - 1} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ k_{1^\prime } \simeq 10^{13.6 - 53,700/2.3RT} {\rm cm}^3 /{\rm mol}\,{\rm sec} $$\end{document}. From thermochemical data of the literature and an “intrinsic value” of E−3⋍ 2 kcal/mol given by Benson, further values of rate constants may be proposed:\documentclass{article}\pagestyle{empty}\begin{document}$$ k_3 \simeq 10^{14 - 9,300/2.3RT} cm^3 /mol\sec $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ k_3 \simeq 10^{13.6 - 15,800/2.3RT} cm^3 /mol\sec $$\end{document}is shown to beE4⋍ 3.5 ± 2 kcal/mol, of the same order as the activation energy of the correspo

ISSN:0538-8066    

DOI:10.1002/kin.550121204

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe kinetic isotope effect (KIE) for carbon and oxygen in the reaction CO + OH has been measured over a range of pressures of air and at 0.2 and 1.0 atm of oxygen, argon, and helium. The reaction was carried out with 21–86% conversion under static conditions, utilizing the photolysis of H2O2as a source of OH radicals. The value of the KIE for carbon varies with pressure and the kind of ambient gas; for air the ratio of the reaction rates12k/13khas the value 1.007 at 1.00 atm and decreases to 0.997 at 0.2 atm; for oxygen and argon over the same pressure range the values are 1.002–0.994 and 1.000–0.991, respectively. The value of the KIE for the CO oxygen atom is16k/18k= 0.990 over the pressure range 0.2–1.0 atm and is independent of the kind of ambient gas. No exchange of the oxygen atoms in the activated complex, followed by decomposition to the starting molecules, was observed. From the mechanistic standpoint the normal KIE observed for carbon at the high pressure is attributed to the initial formation of the activated HOCO radical, whereas the inverse KIE observed at low pressures is a result of the KIE for the reverse reaction HOCO† → CO + OH being greater than that for the forward reaction HOCO†→ CO2+ H. The derived isotopic equilibrium constant for HOCO ⇄CO favors the enrichment of13C in the more st

ISSN:0538-8066    

DOI:10.1002/kin.550121205

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe decadic extinction coefficient of the methyl radical at 216.4 nm and the rate constant for mutual combination were redetermined as:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} \varepsilon (216.4) = (9.5 \pm 0.4) \times 10^3 1./mol\,cm \\ k_2 = (3.2 \pm 0.4) \times 10^{10} 1./mol\sec \\ \end{array} $$\end{document}. The application of the Beer–Lambert law to these measurements was justified experimentally. The absorption spectrum of the methylperoxy radical was characterized as a weak, broad, structureless band, having a maximum at 240 nm with ϵ(240) = 1.55 × 103l./mol cm. The mutual interaction of methylperoxy radicals leads to the generation of methoxy and hydroperoxy radicals as a consequence of the nonterminating interaction\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} 2{\rm CH}_{\rm 3} {\rm OO}^{\rm .} \to 2{\rm CH3O}^{\rm .} + {\rm O}_{\rm 2} \\ {\rm CH}_{\rm 3} {\rm O}^{\rm .} + {\rm O}_2 \to {\rm HCHO + HOO}^{\rm .} \\ \end{array} $$\end{document}. Each derivative radical may consume a significant fraction of the methylperoxy radicals, and either of these cross interactions may be made predominant by a suitable choice of oxygen pressure. The mutual interaction was studied under both conditions. The overall mechanism was analyzed by a precise computational method, and the rate constant of the total mutual interaction\documentclass{article}\pagestyle{empty}\begin{document}$$ 2{\rm CH3O}^{\rm .} \to {\rm all}\,{\rm products} $$\end{document}was estimated as\documentclass{article}\pagestyle{empty}\begin{document}$$ k_4 = (3.5 \pm 0.3) \times 10^8 1./mol\sec $$\end{docume

ISSN:0538-8066    

DOI:10.1002/kin.550121206

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe kinetics of the chlorine isotopic exchange reaction between tetraethylammonium chloride‐36Cl and O,O‐diarylphosphorochloridates (p‐RC6H4O)2POCl or O,O‐diarylphosphorochloridothionates (p‐RC6H4O)2PSCl has been studied in acetonitrile solution. Good Hammett's correlations of the rate constants with Taft's σ0constants were obtained. The values of the reaction constants ρ were found identical for phosphoryl and thiophosphoryl compounds. In comparison with oxygen in the phosphoryl group, the sulfur atom exhibits an electron‐donating effect (Δσ0∼ 0.80). No correlation has been found for the enthalpy and entropy of activation. The effect of the substituents aryloxy groups, oxygen, or sulfur atoms in the phosphoryl group on the kinetics of the SN2‐P reaction is discussed. The reactivity of the investigated compounds is determined by the extent of the positive charge localized on the phosphorus atom. The positive charge is formed by the direct interactions of the substituents with the reaction center and the indirect–intramolecular interactions revealed in the stru

ISSN:0538-8066    

DOI:10.1002/kin.550121207

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe thermal decompositions of azoethane and azoisopropane were studied in a large excess of ethylene in the temperature interval of 523–623 K. It was demonstrated that under such conditions, the bulk of the alkyl radicals react with ethylene. Via measurements on the consumption of the azo compound and on the formation of gaseous nitrogen, it was possible to determine the rate coefficients of the initiation reactions:\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm R - N} = {\rm N - R} \to {\rm N}_{\rm 2} {\rm + 2R}^{\rm .} $$\end{document}. The resulting data were as follows: For azoethane,\documentclass{article}\pagestyle{empty}\begin{document}$$ \log _{10} k_1 (\sec ^{ - 1}) = (15.8 \pm 0.1) - (205.1 \pm 1.5){\rm kJ/mol/2}{\rm .3RT} $$\end{document}. For azoisopropane,\documentclass{article}\pagestyle{empty}\begin{document}$$ \log _{10} k_1 (\sec ^{ - 1}) = (16.2 \pm 0.3) - (196.8 \pm 2.6){\rm kJ/mol/2}{\rm .3RT} $$\end{documen

ISSN:0538-8066    

DOI:10.1002/kin.550121208

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe Cl atom‐initiated oxidation of CH2Cl2and CH3Cl was studied using the FTIR method in the photolysis of mixtures typically containing Cl2and the chlorinated methanes at 1 torr each in 700 torr air. The results obtained from product analysis were in general agreement with those reported by Sanhueza and Heicklen. The relative rate constant for the Cl atom reactions of CH2Cl2and CH3Cl was determined to bek(Cl +CH3Cl)/k(Cl + CH2Cl2) = 1.31 ± 0.14 (2σ) at 298 ±

ISSN:0538-8066    

DOI:10.1002/kin.550121209

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe reaction between formic acid and bromine in strongly acid aqueous media at 298 K\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Br}_2 + {\rm HCOOH} \to {\rm 2Br}^{\rm - } + 2{\rm H}^ + {\rm CO} $$\end{document}was studied by absorption spectrophotometry (λ = 447 nm). Reaction rates, expressed asR= ‐d[Br2]/dt, depend on the concentrations of HCOOH (0.3–2.4M), Br2[(2.7–13.6) × 10−3M], H+(0.03–2.0M), and Br−(up to 0.6M). The mechanismwithk1= 20.2 ± 1.2M−1sec−1, pK2= 3.76, pK3= −1.20, accounts for all experimental observations. Br3−and HCOOH can be considered unreactive within experimental error. Apparent deviations from the basic mechanism at higher acidities can be quantitatively ascribed to the nonide

ISSN:0538-8066    

DOI:10.1002/kin.550121210

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractAt 495°C and a low extent of reaction, ethanal pyrolysis is slightly inhibited by the addition of small quantities of butadiene‐1,3, whereas it is accelerated by more important quantities. The inhibiting effect is interpreted in terms of a free‐radical chain mechanism in which the main chain carriers of ethanal pyrolysis (CH3.free radicals) reversibly add to butadiene‐1,3 and yield penten‐2‐yl (R.) free radicals. These free radicals either react in a metathetical step:or in terminating steps. But butadiene‐1,3 also gives rise to new initiation steps:which account for the accelerating effect. Process (i3) seems to be more important than process (i2) in the experimental conditions, but its nature could not be identified. The results are consistent with literature data and the following value ofk6:\documentclass{article}\pagestyle{empty}\begin{document}$$ k_6 = 10^{12 - 12,000/4,57T} cm^3 /mol\sec $$\end{document}(4.57

ISSN:0538-8066    

DOI:10.1002/kin.550121211

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY