摘要:

AbstractHydrogen, cycloalkene, and bicycloalkyl were found to be the principal products which account for ≈︁97% of all products formed in the gas‐phase radiolysis of water vapor containing low concentrations of cycloalkanes. From the ratios of cycloalkene‐to‐bicycloalkyl yields extrapolated to the zero dose, the self‐ and cross‐disproportionation‐to‐recombination rate constant ratios Δ =kd/kcwere determined for the following 12 reactions: Δ(c‐C5H9,c‐C5H9) = 0.73; Δ(c‐C5D9,c‐C5D9) = 0.58; Δ(c‐C6H11,cC6H11) = 0.59; Δ(c‐C6D11,c‐C6D11) = 0.46; Δ(c‐C5H9,c‐C6H11) = 0.28; Δ(c‐C5D9,c‐C6H11) = 0.28; Δ(c‐C5H9,c‐C6D11) = 0.24; Δ(c‐C5D9,c‐C6D11) = 0.24; Δ(c‐C6H11,c‐C5H9) = 0.33; Δ(c‐C6H11,c‐C5D9) = 0.25; Δ(c‐C6D11,c‐C5H9) = 0.35; and Δ(c‐C6D11,c‐C5D9) = 0.28, where in the case of the cross‐disproportionation the symbol Δ(R1,R2) is used to representkd/kcfor the disproportionation in which radical R1captures a hydrogen (deuterium) atom from radial R2. The geometrical mean rule holds in the cross‐combination reactions of cyclopentyl and cyclohexyl radicals. The kineti

ISSN:0538-8066    

DOI:10.1002/kin.550141002

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractWhile environmental chamber data have been widely used to generate and validate computer models of the chemistry occurring in polluted atmospheres, the effects of the chambers on the gas‐phase chemistry being studied have been poorly characterized. In order to investigate such chamber effects, a series of NOx—air irradiations, with trace levels of organics present to monitor OH radical concentrations, have been carried out in four different environmental chambers (ranging in volume from ∼100 to 40,000 L) at varying temperatures, humidities, pressures, and reaction conditions. In addition, a number of control experiments have been carried out to validate the technique for measuring OH radical levels in these irradiations. The data show that unknown sources of OH radicals are present in all of the chambers studied. The data are consistent with the presence of two distinct radical sources: (1) the photolysis of initially present HONO, whose importance increases with increasing NO2/NO concentration ratios, but which is a minor contributor to the overall radical flux after 30–60 min of irradiation, and (2) a constant (for these NOx—air irradiations) radical source which dominates beyond approximately the first 60 min of irradiation. The radical input rates, after the first ∽30–60 min of irradiation, are independent of the NO concentration, increase with increasing temperature, humidity, and NO2concentration, are proportional to light intensity, and are dependent on the chamber employed. Although the exact nature of this radical source is still undetermined, results of experiments reported here allow a number of possible mechanisms to be ruled, out, and these

ISSN:0538-8066    

DOI:10.1002/kin.550141003

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractEnergetic hydrogen atoms generated by photolysis of HBr or HI react with CDCl3by abstracting either a deuterium atom (1) or a chlorine atom (2):The integral probability of reaction (2) has been measured for several defined initial translational energies of H*, and the phenomenological threshold energy is 31 ± 14 kJ/mol. For initial translational energies in the range of 66–121 kJ/mol, the ratio of the integral probabilities of Cl abstraction and of D abstraction, when normalized to equal numbers of Cl and D atoms, is 2.4 ± 0.3. The interpretation of the integral reaction probabilities in terms of the excitation functions of reactions (1) and (2) is discussed. Measurements of the moderating effect of CO2on reactions (1) and (2) show that CDCl3is slightly more effective than CO2as a moderator of H atoms in the energy range of 90–30 k

ISSN:0538-8066    

DOI:10.1002/kin.550141004

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe oxidation of halotoluenes by hexacyanoferrate(III) in aqueous acetic acid containing perchloric acid (0.5M) at 50°C gave the corresponding aldehyde as the major product, and a small amount of polymeric material. The order with respect to each of the reactants—substrate, oxidant, and acid—was found to be unity. Increasing proportions of acetic acid increased the rate of the reaction. The reaction was influenced by changes in temperature, and the activation parameters have been evaluated. The Hammett plot yielded a ρ+value of −1.8. A kinetic isotope effectkH/kD= 6.0 has been observed. The pathway for the conversion of the halotoluenes to the products has been mechanistically visualized as proceeding through the benzylic radical intermediate, formed in the rate‐determining step of the reaction. The radical undergoes rapid conversion to the

ISSN:0538-8066    

DOI:10.1002/kin.550141005

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe flash photolyses of azo‐n‐propane and azoisopropane in the presence of oxygen have been studied by kinetic spectroscopy. The transient absorption spectra observed in the region of 210–290 nm are assigned to then‐propylperoxy and isopropylperoxy radicals. For then‐propylperoxy radical, εmax= 1148 ± 29 L/mol cm at 242.5 nm and for the isopropylperoxy radical, εmax= 1273 ± 75 L/mol cm at 240 nm. The rate constants for the mutual reactions (7) 2RO2· → products were measured to bek7= (2.0 ± 0.2) X 108L/mol s for then‐propylperoxy radical andk7= (7.8 ± 2.2) X 105L/mol s for the iso

ISSN:0538-8066    

DOI:10.1002/kin.550141006

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractReactions of diphenyl sulfide with the two oxidants peroxydisulfate and peroxydiphosphate are described. With each oxidant, the reaction is first order in the oxidant and zero order in the substrate. The rate of the reaction is also independent of the effect of the substituent. Hydrogen ion catalyzes the reactions. The lack of inhibition of the reaction rate by added acrylamide rules out the possibility of a radical reaction initiated by the homolysis of the peroxyanions. From the effect of [H+] on the oxidation rates, the active species involved in the reactions have been determined. The redox reaction is essentially proceeding via hydrolysis of the protonated peroxy anions in a rate‐determining step, followed by a fast step involving the oxidation of diphenyl sulfide to diphenyl sulfoxide. This has been confirmed by estimating the hydrolyzed products in each case and also by the product analyse

ISSN:0538-8066    

DOI:10.1002/kin.550141007

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe flash photolysis resonance fluorescence technique has been used to measure the rate constant for the reactionover the temperature range of 250–370 K. The present results are in excellent agreement with three very recent studies, and the combined data set can been used to derive the expressionsimilar to that currently used in atmospheric modeling applications.A summary of our computer simulation of this reaction system is presented. The results of the computations indicate the absence of secondary reaction complications in the present work while revealing significant problems in the earlier (pre‐1980) studies of the title react

ISSN:0538-8066    

DOI:10.1002/kin.550141008

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550141001

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY