摘要:

AbstractThe quantum yields of SO3formation have been determined in pure SO2and in SO2mixtures with NO, CO2, and O2using both flow and static systems. In separate series of experiments excitation of SO2was effected within the forbidden band, SO2(3B1) ←\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm SO}_2 (\tilde X,^1 A_1 ) $$\end{document}, and within the first allowed singlet band at 3130 Å. The values of Φ SO 3were found to be sensitive to the flow rate of the reactants. These results and the apparently divergent quantum yield results of Cox [10], Allen and coworkers [24, 26, 29], and Okuda and coworkers [11] were rationalized quantitatively in terms of the significant occurrence of the reactions SO + SO3→ 2SO2(2), and 2SO → SO2+ S [or (SO)2] (3), in experiments of long residence time. From the present rate data, values of the rate constants were estimated,k2=(1.2±0.7) × 106;k3=(5±4) × 105l˙/mole · sec. Φ SO 3values from triplet excitation experiments at high flow rates of NOSO2and CO2SO2mixtures showed the sole reactant with SO2leading to SO3formation in this system to be SO2(3B1); SO2(3B1) + SO2→ SO3+ SO(3Σ−) (la);k 1 a=(4.2±0.4) × 107l./mole · sec. With excitation of SO2at 3130 Å both singlet and triplet excited states play a role in SO3formation. If the reactive singlet state is1B1, the long‐lived fluorescent state, SO2(1B1) + SO2→ SO3+ SO (1Δ or3Σ−) (lb), thenk 1 b=(2.2±0.5) × 109l./mole · sec. From the observed inhibition of SO 3 −formation by added nitric oxide, it was found that the SO3‐forming triplet state, generated in this singlet excited SO2system, had a relative reactivity toward SO2and NO which was equal within the experimental error to that observed here for the SO2(3B1) species. Either SO2(3B1) molecules were created with an unexpectedly high efficiency in 3130 Å excited SO2(1B1) quenching collisions, or another reactive triplet (presumably3A2or3B2

ISSN:0538-8066    

DOI:10.1002/kin.550070202

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe kinetics of chlorine atom abstraction from the chloromethanes (CM)CCl4, CHCl3, and CH2Cl2by radiolytically generated cyclohexyl radicals has been studied in the liquid phase by a competitive method. The halogen abstraction data have been put on an absolute basis by comparing the rates of the metathetical reactions with the known rate of addition of cyclohexyl radicals to C2Cl4.The following Arrhenius parameters were obtained:TextCMlogA(CM)/A(C2Cl4)E(CM)E(C2Cl4)(kcal/mole)logA(CM)(1./mole·sec)E(CM) (kcal/mole)Temperaure Range(°K)CCl40.72±0.02−1.42±0.059.40±0.085.88±0.15333–453CHCl30.77±0.062.86±0.019.45±0.1210.16±0.11392–492CH2Cl20.56±0.126.37±0.279.42±0.1813.67 ± 0.37463–543The error limits are the standard deviations from least mean square Arrhenius plots.The possible application of the Evans–Polanyi relationship to chlorine atom abstraction react

ISSN:0538-8066    

DOI:10.1002/kin.550070203

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe π*←nexcited state kinetics of hexafluoroacetone are reinvestigated in the presence of a vibrational relaxer and sufficient triplet state quencher so that only the reactions of the electronically excited upper singlet state are examined. From a Stern–Volmer type analysis it is concluded that vibrational relaxation of the initially formed vibrationally and electronically excited upper singlet state isviaa multistage collisional mechanism. An activation energy of about 6 kcal/mole is reported for the unimolecular decomposition of the upper singlet s

ISSN:0538-8066    

DOI:10.1002/kin.550070204

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractSpectrophotometric methods have been used to obtain rate laws and rate parameters for the following reactions:withka,kb,Ea,Ebhaving the values 85±5 l./mole · s, 5.7±0.2 s−1(both at 298.2°K), and 56±4 and 66±2 kJ/mole, respectively.withkc=0.106±0.004 l./mole ·s at 298.2°K andEc=67±2 kJ/mole.withkd=(3.06 ±; 0.15) × 10−3l./mole ·s at 298.2°K andEd=66±2 kJ/mole.Mechanisms for these reactions are discussed and compared

ISSN:0538-8066    

DOI:10.1002/kin.550070205

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractRate equations have been deduced for two possible mechanisms for the reactions ofN‐methyl‐N‐nitrosoaniline in acid solution, namely, (1) for the generally acceptedintermolecularmechanism which involves denitrosation followed byC‐nitrosation and (2) a mechanism involvingintramolecularrearrangement which takes place concurrently with denitrosation. The observed rate constants obtained under various experimental conditions are consistent only with mechanism (2). In particular the question of halide ion catalysis differentiates clearly between the two mechanisms. Mechanism (1) predicts a first‐order dependence upon chloride (or other halide) ion under all conditions, whereas (2) allows a first‐order chloride ion dependence only in the presence of a large excess of a “nitrite trap” such as sulphamic acid, urea, hydrazoic acid, hydroxylamine, etc., whereas at the other limit of high concentration of addedN‐methylaniline, the rate constants should be independent of the halide ion concentration. The predictions based on mechanism (2) are all borne

ISSN:0538-8066    

DOI:10.1002/kin.550070206

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractHigh‐temperature (>1000°K) pyrolysis of acetaldehyde (∼1% in an atmosphere of pure nitrogen) was examined in a turbulent flow reactor which permits accurate determination of the spatial distribution of the stable species. Results show that the products in order of decreasing importance are CO, CH4, H2, C2H6, and C2H4. Rates of formation were consistent with the Rice–Herzfeld mechanism by including reactions to explain C2H4formation and the possible presence of ketene. A steady‐state treatment of the complete mechanism indicates that the overall reaction order decreases from\documentclass{article}\pagestyle{empty}\begin{document}$ \frac{3}{2} $\end{document}to 1, which is supported by the new experimental data. Using earlier low‐temperature results, the rate constant for the reaction CH3CHO → CH3+ CHO (1) was found ask1=1015.85±0.21exp (−81,775±1000/RT) sec−1. Also, data for the ratio of rate constants for reactions CH3CHO + CH3→ CH4+ CH3CO (4) and 2CH3→ C2H6(6) were fitted to the empirical expressionk4/k61/2=10−13.89±0.03T6.1exp(−1720±70/RT) (cm3/mole·sec)1/2and causes for the curvature are discussed. The noncatalytic effect of oxygen on acetaldehyde pyrolysis at

ISSN:0538-8066    

DOI:10.1002/kin.550070207

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe kinetics of decarbonylation of [Ir(CO)(dp)2]Cl and [IrCl(CO)2(Ph3P)2] has been studied in different solvents, at temperatures between −25° and +70°C, by means of reactors of defined fluid dynamics which allow a separation to be made between “physical” and “chemical” rate constants. Chemical rate constants have been found to depend markedly on the diffusion coefficients of carbon monoxide in the various solvents. The process of decarbonylation has been described, for both reactions, by the sequence: structural isomerization, characterized by a very low preexponential factor, decomposition of the less stable isomer against the solvent's barrier, and diffusion of carbon monoxide to the gas–liquid interface. The kinetic problems involved in the determination of rate constants and their implications have be

ISSN:0538-8066    

DOI:10.1002/kin.550070208

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe kinetics of the thermal bromination reaction\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Br + CF}_{\rm 3} {\rm I} \to {\rm IBr + CF}_{\rm 3} {\rm Br} $$\end{document}have been studied in the range of 173–321°C. For the stepwe obtain\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log}\,k_{11} \,({\rm cm}^{\rm 3} /{\rm mole} \cdot {\rm sec) = (13}{\rm .19) - (10840} \pm {\rm 460)/}\theta $$\end{document}where θ=2.303RTcal/mole. From the activation energy for reaction (11), we calculate that\documentclass{article}\pagestyle{empty}\begin{document}$$ D({\rm CF}_{{\rm 3}^{\rm - } } {\rm I) = 52}{\rm .6} \pm {\rm 1}{\rm .1}\,{\rm kcal/mole}\,{\rm at 25}{}^{\rm 0}{\rm C} $$\end{document}This is compared with previously published values ofD(CF3−I). The relevance of the result to published work on kcfor a combination of CF3radicals is disc

ISSN:0538-8066    

DOI:10.1002/kin.550070209

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe overall photobromination reactions\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Br}_{\rm 2} + {\rm R}_{\rm F} {\rm I} \to {\rm IBr} + {\rm R}_{\rm F} {\rm Br} $$\end{document}have been studied using a competitive technique. Relative Arrhenius parameters were obtained for the rate‐determining stepThese were placed on an absolute basis using previous‐absolute values ofAandEfor RFI=CF3I. The activation energies were used to calculate bond dissociation energiesD(RI) with the following results:TextRF−E16D(RF−I)(kcal/mole)CF3I10.852.6C2F5I8.850.6n‐C3F7I7.449.2i‐C3F7I7.549.2n‐C4F9I6.748.4E16from [1]TheD(R F −I) are compared with relatedD(RI) and it is concluded that for a given alkyl group RHand the corresponding perfuloroalkyl group RF,D(R H −I)>D(R F −I) whereas it has previously been found thatD(R H

ISSN:0538-8066    

DOI:10.1002/kin.550070210

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractA flow tube method has been used to determine rate constants for the elementary reactions:Oxygen atoms were produced by adding a small excess of NO to a stream of partially dissociated nitrogen, and their reaction with hydrogen halide was monitored by observing the intensity of the NO + O afterglow. Experiments were carried out at temperatures from 293 to 440°K with HCl, and from 267 to 430°K with HBr. The role of secondary reactions was minimised and the residual effects were allowed for. The rate constants for the primary reactions could be matched by Arrhenius expressions:\documentclass{article}\pagestyle{empty}\begin{document}$$ k_{1a} = 2.5\left({_ - ^ + } \right.\left. {{}_{0.8}^{1.2} } \right) \times 10^{ - 12} \,{\rm exp}\frac{{{\rm ( - 5}{\rm .9} \pm {\rm 0}{\rm .3}\,{\rm kcal/mole)}}}{{RT}} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ k_{1b} = 4.0( \pm 0.7) \times 10^{ - 12} \,{\rm exp}\frac{{{\rm ( - 2}{\rm .7} \pm {\rm 0}{\rm .1}\,{\rm kcal/mole)}}}{{RT}} $$\end{document}where the units are cm3/molec·sec and the errors correspond to a standard deviati

ISSN:0538-8066    

DOI:10.1002/kin.550070211

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY