摘要:

AbstractThe system iodate‐peroxide‐manganese(II)‐butanone is a member of the Briggs–Rauscher set of oscillators. The stoichiometry and variation of the oscillation period with concentration for each component is studied under batch conditions. The system is simulated using the skeleton mechanism of earlier workers and reproduces the observed variation in oscillation period. Examination of the roles of the reaction steps shows that there are significant differences from those found using malonic acid. Iodine is stored during the low iodide regime and utilized during the high iodide regime, and different overall reactions occur during the two regimes. © 1994 John Wiley&S

ISSN:0538-8066    

DOI:10.1002/kin.550261202

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractIn many decomposition reactions, the reaction velocity can be described as a product of two functions: a temperature dependent partK(T) and the kinetic functionf(1 – α), whereTdesignates the temperature and α the fraction of reactant that has decomposed. The physical interpretation of these functions is discussed for both solid and homogeneous systems. A method is described by whichf(1 – α) andK(T) can be determined from kinetic data. The mechanism of decomposition can subsequently be identified which should be consistent with the derived kinetic parameters. The method has been applied to analyze the kinetics of the thermal decomposition of nitromethane. © 1994 John Wiley&So

ISSN:0538-8066    

DOI:10.1002/kin.550261203

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractWith a view to clarifying analogies and differences between the mechanisms involved in the nitrosation of amino acids and secondary amines, we studied the kinetics of the nitrosation of five imino acids (azetidine‐2‐carboxylic acid, pyrrolidine‐2‐carboxylic acid, piperidine‐2‐carboxylic acid, piperidine‐3‐carboxylic acid, and piperidine‐4‐carboxylic acid) and of the ethyl esters of three of them. Reaction kinetics were determined by the initial rate method, by spectrophotometric monitoring of the concentration of nitroso amino acid formed. The presence of the COO−group in the amino acids opens a new mechanistic route for the nitrosation of the secondary amino group: a nitrosyl carboxylate formed initially acts as an internal nitrosating agent, resulting in intramolecular migration of N  O from the carboxylate group to the secondary amino group. The observed order of the α−, β−, and γ‐amino acids as regards the ease ofN‐nitrosation by this route is explained in terms of the relative energies of (a) the equatorial and axial orientations of the CringCcarboxylbond, and (b) the chair and boat forms of the pipe

ISSN:0538-8066    

DOI:10.1002/kin.550261204

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractNanosecond laser flash photolysis (λ = 355 nm) of an aqueous solution of 3‐chloro‐3‐p‐chlorophenyldiazirine in isooctane produces a transient absorption at 310 nm due to the formation of the carbene. In the presence of 2‐vinylpyridine, a second transient with a broad absorption band peaking at 520 nm grows in. This absorption is attributed to 2‐vinylpyridinium ylide. The ylide decays with a lifetime equal to 33 µs at 25°C independent of the concentration of 2‐vinylpyridine. As the ylide decays, there is a concomitant growth of an absorption at 330 nm, attributed to the formation of inodolizine. The activation parameters for the 1,5‐dipolar cyclization of the ylide to indolizine were determined;Ea= 12.1 kcal mol−1and logA= 13.4. © 1994

ISSN:0538-8066    

DOI:10.1002/kin.550261205

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe gas‐phase reaction of ozone with unsaturated alcohols in air has been investigated at atmospheric pressure and ambient temperature (288–291 K). Cyclohexane was added to scavenge the hydroxyl radical which forms as a product of the ozone–unsaturated alcohol reaction. The reaction rate constants, in units of 10−18cm3molecule−1s−1, are 16.2 ± 0.7 for (±) 3‐buten‐2‐ol, 17.9 ± 1.8 for 1‐penten‐3‐ol, 10.0 ± 0.3 for 2‐methyl‐3‐buten‐2‐ol, 169 ± 25 forcis‐2 penten‐1‐ol, and 251 ± 41 for 2‐buten‐1‐ol (mixture of isomers). Substituent effects on reactivity are discussed. The reactivity of unsaturated alcohols towards ozone is similar to that of their alkene structural homologues. Implications of these results with respect to the atmospheric persistence of unsaturated alcohols

ISSN:0538-8066    

DOI:10.1002/kin.550261206

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractRate constants for the gas‐phase reactions of O3with the sesquiterpenes α‐cedrene, α‐copaene, β‐caryophyllene, α‐humulene, and longifolene, and with the monoterpenes limonene, terpinolene, α‐phellandrene, and α‐terpinene, have been measured using a relative rate technique at 296 ± 2 K and atmospheric pressure of air. The rate constants obtained (in units of 10−17cm3molecule−1s−1) are: limonene, 20.1 ± 5.1; terpinolene, 188 ± 67; α‐phellandrene, 298 ± 105; α‐terpinene, 2110 ± 770; α‐cedrene, 2.78 ± 0.71; α‐copaene, 15.8 ± 5.6; β‐caryophyllene, 1160 ± 430; α‐humulene, 1170 ± 450; and longifolene,<0.07, where the indicated errors include the estimated overall uncertainties in the rate constants for the reference organics. Hydroxyl radical formation yields were also determined for the O3reactions with the sesquiterpenes, of 0.67 for α‐cedrene, 0.35 for α‐copaene, 0.06 for β‐caryophyllene, and 0.22 for α‐humulene, all with estimated overall uncertainties of a factor of ca. 1.5. The tropospheric lifetimes of the sesquiterpenes du

ISSN:0538-8066    

DOI:10.1002/kin.550261207

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe oxidation kinetics of NO by O2in aqueous solution was observed using a stopped flow apparatus. The kinetics follows a third order rate law of the formk· [NO]2· [O2] in analogy to gas‐phase results. The rate constant at 296 K was measured as (6.4 ± 0.8) · 106M−2s−1with an activation energy of 2.3 kcal/mol and a preexponential factor of (4.0 ± 0.5) · 108M−2s−1. The rate constant displays a very slight pH dependence corresponding to less than a factor of three over the range 0 to 12. The system NO/O2in aqueous solution is an efficient nitrosating agent which has been tested using phenol as a substrate over the pH range 0 to 12. The rate limiting step leading to formation of 4‐nitrosophenol is the formation of the reactive intermediate whose competitive hydrolysis yields HONO or NO2−. The absence of NO3−in the autoxidation of NO, the exclusive presence of NO2−as a product of the nitrosation reaction of phenol, and the kinetic results of the N3−trapping experiments point towards N2O3as the reactive intermediate. ©

ISSN:0538-8066    

DOI:10.1002/kin.550261208

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550261201

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY