摘要:

AbstractAn experimental and modeling study of irradiated toluene–NOx–air, toluene–benzaldehyde–NOx–air, and cresol–NOx–air mixtures at part‐per‐million concentrations has been carried out. These mixtures were irradiated at 303 ± 1 K in a 5800‐liter Teflon‐lined, evacuable environmental chamber, with temperature, humidity, light intensity, spectral distribution, and the concentrations of O3, NO, NO2, toluene, PAN, formaldehyde, benzaldehyde,o‐cresol,m‐nitrotoluene, and methyl nitrate beingmonitored as a function of time. For the toluene and toluene–benzaldehyde–NOx–air runs a variety of initial reactant concentrations were investigated. Cresol–NOx–air runs were observed to be much less reactive in terms of O3formation and NO to NO2conversion rates than toluene–NOx–air runs, with the relative reactivity of the cresol isomers being in the order meta » ortho>para. The addition of benzaldehyde to toluene–NOx–air mixtures decreased the reactivity, in agreement with previous studies. Alternative mechanistic pathways for the NOxphotooxidations of aromaticsystems in general are discussed, and the effects of varying these mechanistic alternatives on the model predictions for the toluene ando‐cresol–NOx–air systems are examined. Fits of the calculations to most of the experimental concentration–time profiles could be obtained to within the experimental uncertainty for two of the mechanistic options considered. In both cases it is assumed that (1) O2adds to the OH–toluene adduct ∼75% of the time forming, after a further addition of O2, a C7bicyclic peroxy radical, and (2) this C7bicyclic peroxy radical reacts with NO ∼75% of the time to ultimately form α‐dicarbonyls and conjugated γ‐dicarbonyls (e.g., methylglyoxal + 2‐butene‐1,4‐dial) and ∼25% of the time to form organic nitrates. The major uncertainties in the mechanisms concern (1) the structure of the bicyclicperoxy intermediate, and (2) the γ‐dicarbonyl photooxidation mechanism. Good fits to theo‐cresol concentration–time profiles in the toluene–NOxruns are obtained if it is assumed thato7‐cresol reacts rapidly with NO3radicals. However, it is observed that the model underpredicts nitrotoluene yields by a factor of ∼10, but this is in any case a minor product. It is concluded that further experimental work will be required toadequately validate

ISSN:0538-8066    

DOI:10.1002/kin.550121102

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe kinetics of bromination of several aromatic compounds (anilides, anisoles, and phenols) was investigated in 80% aqueous acetic acid (v/v) in the temperature range 20–50°C usingN‐bromosuccinimide (NBS) as the reagent. The reaction was found to be first order in the aromatic substrate (ArH), and zero order in NBS, the overall order being 1. Stoichiometry of the reaction was 1:1. An increase in solvent polarity increased the reaction rate, and chloride ions were found to be specific catalysts for the reaction. Arrhenius activation energy remained almost constant for all the substrates. A probable mechanism explaining all these observed facts was proposed. The mechanism involved an attack by Br+or more probably by a solvated Br+ion on the aromatic subst

ISSN:0538-8066    

DOI:10.1002/kin.550121103

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe rate of the reactionwas determined in an isothermal discharge flow reactor with a combined ESR–LMR detection under pseudo‐first‐order conditions in HO2. The rate constant was identical in experiments with two different HO2sources: F + H2O2and H + O2+ M. The absolute rate constant atT= 293 K was measured as\documentclass{article}\pagestyle{empty}\begin{document}$$ k_1 (293K) = (4.6 \pm 1)10^{12} cm^3 /mol\sec $$\end{document}In the range 2 ≤pmbar ≤ 17 no pressure dependence fork1

ISSN:0538-8066    

DOI:10.1002/kin.550121104

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe kinetics of oxidation of benzyl alcohol and substituted benzyl alcohols by sodiumN‐chloro‐p‐toluenesulfonamide (chloramine‐T, CAT) in HClO4(0.1–1 mol/dm3) containing Cl−ions, over the temperature range of 30–50°C have been studied. The reaction is of first order each with respect to alcohol and oxidant. The fractional order dependence of the rate on the concentrations of H+and Cl−suggests a complex formation between RNCl−and HCl. In higher acidic chloride solution the rate of reaction is proportional to the concentrations of both H+and Cl7hyphen;. The observed solvent isotope effect (k D 2O/k H 2O) is 1.43 at 30°C. The reaction constant (p= −1.66) and thermodynamic parameters are evaluated. Rate expressions and probable mechanisms for the observed

ISSN:0538-8066    

DOI:10.1002/kin.550121105

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractDi‐tert‐butylnitroxide (DTBN) is the simplest of the stable nitroxide radicals and is only consumed at temperatures higher than 90°C or in the presence of very reactive substrates. The pyrolysis of DTBN in solution gives, at least at low conversion, 2‐methyl‐2‐nitrosopropane and di‐tert‐butylnitroxide‐tert‐butyl ether. The reaction involves, as the rate‐limiting step, the cleavage of the CN bond. This reaction takes place with an activation energy of 33 kcal/mol. DTBN is stable in the presence of styrene, aldehydes, hydrogen peroxide, α‐methyl‐N‐ethyl nitrone, phenol, and triphenylmethane. On the other hand, it reacts readily with diethylhydroxylamine, ascorbid acid, ethanethiol, and hexanethiol. For the two former compounds the reaction involves a hydrogen transfer as the rate‐determining step, and the reaction proceeds, a low conversion, with simple second‐order kinetics. The reaction with the thiols is comple

ISSN:0538-8066    

DOI:10.1002/kin.550121106

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe addition reactions of CCl3radicals withcis‐C2Cl2H2,trans‐C2Cl2H2, and C2Cl3H in liquid cyclohexane–CCl4mixtures were studied between 323 and 448 K. The Arrhenius parameters of these reactions were competitively determined versus H‐atom transfer from cyclohexane and addition to C2Cl4. The present data and the data obtained in previous liquid and gas phase studies show that the reactivities displayed in addition reactions of different radicals with chloroethylenes reflect primarily variations in activation energies rather than inAfactors. The activation energies for the addition of CCl3, CF3, and CH3radicals to chloroethylenes appear, to a large extent, to be determinedby the stability of the adduct radicals. Comparison of the reactivity trends in the addition reactions of chloro‐ and fluoro‐substitutedethylenes indicates that these two electron‐withdrawing substituentshave a converse effect on the reactivity of electrophilic radicals. This behavior is ascribed to the strong mesomeric effect of vinylic chlor

ISSN:0538-8066    

DOI:10.1002/kin.550121107

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550121101

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY