摘要:

AbstractKinetic studies of the transfer of hydrogen from 9,10‐dihydrophenanthrene to anthracene were done at 350°C in the liquid phase. Principal products were phenanthrene and 9,10‐dihydroanthracene. Autocatalysis occurred at low extents of reaction, where H‐transfer from 9,10‐dihydroanthracene to anthracene caused an increase in free radical concentrations. At higher extents of reaction, 9,10‐dihydroanthracene inhibited rates by diverting intermediate 9‐hydrophenanthryl radicals back to reactants. A quantitative kinetic model based on literature rate and thermodynamic data fits the observations well. A key net reaction is the transfer of an H‐atom from a radical (9‐hydrophenanthryl) to a molecule (anthracene). It is shown that this process does not involve a free H‐atom intermediate. The derived rate constant for this exothermic process (7.5 × 103M−1s−1) is considerably greater than that for the related, but thermoneutral H‐transfer between anthrac

ISSN:0538-8066    

DOI:10.1002/kin.550210602

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe decomposition of 1‐chloro‐1,1‐difluoroethane by a radical chain reaction has been studied in a flow reactor in the temperature range from 503 to 773 K. For the initiation of the chain small amounts of added chlorine were photolyzed with a XeCl laser (λ = 308 nm). The formation of the dehydrochlorination and chlorination products, vinylidene fluoride, and 1,2‐dichloro‐1,1‐difluoroethane respectively, is described by a kinetic model. Arrhenius parameters for the two abstraction reactions\documentclass{article}\pagestyle{empty}\begin{document}$${\rm CI + CH}_{\rm 3} {\rm CCIF}_{\rm 2} {\hbox to 25pt{\rightarrowfill}} {\hskip-18pt ^{K_2 }}{\hskip1em} {\rm HCI + CH}_{\rm 2} {\rm CCIF}_{\rm 2}$$\end{document}and\documentclass{article}\pagestyle{empty}\begin{document}$${\rm CI + CH}_{\rm 2} {\rm CICCIF}_{\rm 2} {\hbox to 25pt{\rightarrowfill}} {\hskip-18pt ^{K_7 }}{\hskip1em} {\rm HCI + CHCICCIF}_{\rm 2}$$\end{document}were determined by a competition method:\documentclass{article}\pagestyle{empty}\begin{document}$$\log _{10} (k_2 /cm^3 {\rm mol}^{{\rm - 1}} {\rm s}^{{\rm - 1}} = (13.6 \pm 0.1) - (9200 \pm 300)/4.576T$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$\log _{10} (k_7 /cm^3 {\rm mol}^{{\rm - 1}} {\rm s}^{{\rm - 1}} = (13.7 \pm 0.1) - (6500 \pm 200)/4.576T$$\end{document}Experimental and modeling results are discussed with respect to former studies on the thermal reaction of 1‐chloro‐1,

ISSN:0538-8066    

DOI:10.1002/kin.550210603

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe kinetics of oxidation of 2,2′‐azinobis‐(3‐ethylbenzothiazole‐6‐sulphonate) (ABTS) by the inorganic peroxides, peroxomonosulphate, peroxodisulphate, peroxodiphosphate, and hydrogen peroxide were investigated in aqueous solution. The kinetics of formation of the radical cation, ABTS.+, on one‐electron abstraction by these peroxides and the further reaction of ABTS.+with higher concentrations of these peroxides at longer time scale were studied by following the growth and decay of the radical cation, ABTS.+at 417 nm. The rate of formation of ABTS.+was found to obey a total second‐order, first‐order each in [ABTS] and [peroxide], except for H2O2, which reacted through Michaelis‐Menten kinetics. All the peroxides investigated were found to react with ABTS.+; however peroxodisulphate alone oxidized ABTS.+to the dication (ABTS++), the other peroxides reacted via ionic mechanism, probably forming sulphoxide and sulphone as products. The kinetics of decay of the radical cation, ABTS.+, was also found to follow a total second‐order, first‐order each in [ABTS.+] and [peroxide], except peroxodiphosphate the reaction of which obeyed Michaelis‐Menten kinetics. The effect of pH and temperature were also investigated in all the systems and the kinetic and thermodynamic parameters were evaluated and discussed with sui

ISSN:0538-8066    

DOI:10.1002/kin.550210604

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe kinetics of oxidation of a number of ortho, meta, and para substitutedS‐phenylmercaptoacetic acids byN‐Chloro‐3‐Metyl‐2,6‐Diphenylpiperidin‐4‐one (NCP) has been studied in buffered ethanol‐water (75:25 v/v) of pH 5.46. The reaction is of first order each in [oxidant] and [substrate]. The rate constant decreases with increase in pH from 5.22 to 5.70. The reaction is accelerated by electron releasing and retarded by electron withdrawing substitutents. The ρ value obtained for this reaction is −1.88 at 10°C with a good correlation coefficient of 0.99 showing an electron deficient transition state. The effect of ortho substitutents also i

ISSN:0538-8066    

DOI:10.1002/kin.550210605

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractRates of reaction for the alkaline hydrolysis of various hydroxamic acids in the presence of cetyltrimethylammonium bromide have been determined. Empirical reaction orders of zero, one‐half, and one were found for the hydroxamic acids depending upon reaction conditions and substrate structure.N‐methylhydroxamic acids exhibited only first‐order kinetics. The results are consistent with the Michaelis‐Menten rate e

ISSN:0538-8066    

DOI:10.1002/kin.550210606

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe kinetics of reaction of substituted 2‐aminobenzothiazoles and phenacyl bromide have been followed conductometrically and in some cases, argentometrically. Both the methods produced almost the same rate constants. Substituents at position 5 of the benzothiazole nucleus behave like para substituents of the benzene ring. A correlation with Hammett σpsubstituent constants has been obtained with a rho value of −1.04. The rate data of quaternization reaction of 4, 5, and 6 substituted 2‐aminobenzothiazoles with phenacyl bromide have been correlated withFk,Rk, andVwvalues by multiple regression analysis with the equation suggested by Williams and Norrington and modified by us. The values are found to correlate well with the equation, logk= −4.4979 − 0.4815fjFk+ 0.5933rjRk

ISSN:0538-8066    

DOI:10.1002/kin.550210607

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractAn earlier correlation between isolated CH stretching frequencies,v isCH, and experimental CH bond dissociation energies, in hydrocarbons, fluorocarbons, and CHO compounds, is updated. A stabilization energy,E vS, which reflects only the properties of the radical, is defined by the deviation of a point from the above correlation.E vSvalues for a variety of radicals are listed and discussed. In HCN and HCO compoundsE vSis low or negligible, due to the lowv isCHfound in these compounds. The conventional definition ofESthen represents a serious misnomer, which distracts attention from the probable source of discrepancies between experimental andab initiovalues of DH°(CH), namely, the parent molecules. Stereo electronic effects concerned with the breaking of CH bonds are predicted in a variety of situations.Some experimental determinations of DH°(CH), viz., in C2H4, HCOOH, CH3CHO, CH3NH2, are considered to be probably in error.Schemes for partitioning energies of atomization into ‘standard’ or ‘intrinsic

ISSN:0538-8066    

DOI:10.1002/kin.550210608

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractPyrogallol (1,2.3‐benzentriol,1) reacts with dioxygen in weakly alkaline solutions to form purpurogallin (2,3,4,6‐tetrahydroxy‐5H‐benzocycloheptene‐5‐one,2) which then reacts to form purpurogalloquinone (3) which then decays to a product absorbing at 440 nm. The formation of 3 requires 1.5 mol O2per mol1, and 1.0 mol per mol2. No O2is consumed during the decay of3, and this reaction, being insensitive to O2concentrations and the presence of both superoxide dismutase (SOD) and catalase, does not appear to be an oxidation. The first‐order rate of decay of3decreases with increasing pH.1and3react at pH 9.0 with a second‐order rate constant of ca. 100 M−1s−1. SOD inhibits the oxidation of1and2. Slight and variable apparent inhibition of the oxidation of2and3by SOD may be due to trace impurities in2, but not contamination by1. The peak concentration of3is attained more rapidly during the oxidation of1than during the oxidation of2. A kinetic scheme based on parallel oxidation of1by dioxygen and superoxide, and it which the semiquinone of1oxidizes2, is partially successful in simulating the observ

ISSN:0538-8066    

DOI:10.1002/kin.550210609

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550210601

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY