摘要:

AbstractRates of solvolysis of ions [Co(3Rpy)4Cl2]+withR= Me and Et have been measured over a range of temperatures for a series of water‐rich water + methanol mixtures to investigate the effect of changes in solvent structure on the solvolysis of complexes presenting a largely hydrophobic surface to the solvent. The variation of the enthalpies and entropies of activation with solvent composition has been determined. A free energy cycle relating the free energy of activation in water to that in water + methanol is applied using free energies of transfer of individual ionic species from water into water + methanol. Data for the free energy of transfer of chloride ions ΔG t∘(Cl−) from both the spectrophotometric solvent sorting method and the TATB method for separating ΔG t∘(salt) into ΔG t∘(i) for individual ions are used: irrespective of the source of ΔG t∘(Cl−), in general, −ΔG t∘(Co(Rpy)4Cl2+)>−ΔG t∘(Co(Rpy)4Cl2+), where Rpy = py, 4Mepy, 4Etpy, 3Etpy, and 3Mepy, showing that changes in solvent structure in water‐rich water + methanol mixtures generally stabilize the cation in the transition state more than the cation in the initial state for this type of complex ion. A similar result is found when the free energy cycle is applied to the solvolysis of the dichloro (2,2′,2″‐triaminotriethylamine)cobalt(III) ion. The introduction of a Me or Et group on the pyridine ring in [Co(Rpy)4Cl2]+has little influence on the difference {ΔG t∘(Co(Rpy)4Cl2+)−ΔG t∘(Co(Rpy)4Cl2+)}

ISSN:0538-8066    

DOI:10.1002/kin.550220902

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe stability of some Schiff‐bases formed between PLP and different amino acids has been investigated in a wide range of pH. The kinetic constants of formation of these compounds and their hydrolysis rate constants have been determined. Results show that the α‐position of the carboxyl group of amino acid plays an important role on the mechanism of water attack upon the CNbond. The absence of ionic groups in the surroundings of that bond must be an important factor of stability. Bulky hydrophobic substituents in the amino acid, near the amine part, protect the imine bond against hy

ISSN:0538-8066    

DOI:10.1002/kin.550220903

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractRecent experimental results on the thermal decomposition and the reverse recombination of alkyl and haloalkyl peroxynitrates are modelled with an SACM formalism. The molecules RO2NO2with R = CH3, CF3, CF2Cl, CFCl2, CCl3, and C2H5are considered. Detailed and simplified reduced falloff expressions are compared. Limiting low (

ISSN:0538-8066    

DOI:10.1002/kin.550220904

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe thermal decomposition ofn‐pentane has been investigated in the temperature range 737 to 923 K. Making various assumptions, the detailed distribution of major products (methane, ethane, ethene, propene, and 1‐butene) is used to evaluate the rate constant for the unimolecular isomerizationwhich proceeds via a five‐membered, cyclic transition state. Two alternative sets of assumptions are used. Common to both of them are assumptions concerning the thermochemistry and rate constants for decomposition of the C5H11radicals. Method 1 assumes that all secondary CH bonds are equally reactive towards hydrogen abstraction in which case, in addition to the value of

ISSN:0538-8066    

DOI:10.1002/kin.550220905

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractIn lowest approximation, a certain chemical reaction is described by a system of first‐order linear differential equations with unknown constant coefficients. One can therefore write down an expression for the state of the system at timet, and from this find the endpoint of the reaction in terms of the initial state and the rate constants. The relative values of some rate constants can then be estimated from experimental data.A better approximation in which the differential equations are nonlinear is also considered, and it turns out that because of symmetry in the reaction, the relationship between the final state and the ratios of the rate constants is unchanged. Although the differential equations now appear much less tractable, the problem of relating the rate constants to the endpoint of the reaction can be formulated and solved in terms of probabilities.The results illustrate an important property of reaction schemes in which some of the steps are reversible. More generally, this is a property of differential equations: provided that they continue to satisfy certain linear constraints, the parameters of a linear system of ordinary differential equations can vary without affecting the asymptotic solutio

ISSN:0538-8066    

DOI:10.1002/kin.550220906

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe decomposition of alkaline hydrogen peroxide solutions at 20°C has been studied in the presence of both supported iron catalysts and in systems with iron initially in solution. Studies with an iron‐alumina supported catalyst showed the decomposition reaction was first order with respect to total peroxide concentration, while studies with alkaline Fe3+produced more complex behavior. This has been attributed to the presence of at least two distinct catalytically active iron species. The first species is highly active and gives rise to high initial rates of reaction. A decrease in concentration of this species is observed together with an increase in concentration of a second, less active, iron species. The catalytic behavior of this “aged” iron species was found to be very similar to that of the supported iron ca

ISSN:0538-8066    

DOI:10.1002/kin.550220907

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550220908

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe kinetics of the gas‐phase reactions of allyl chloride and benzyl chloride with the OH radical and O3were investigated at 298 ± 2 K and atmospheric pressure. Direct measurements of the rate constants for reactions with ozone yielded values of

ISSN:0538-8066    

DOI:10.1002/kin.550220909

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe kinetics and nitroarene product yields of the gas‐phase reactions of naphthalene‐d8, fluoranthene‐d10, and pyrene with OH radicals in the presence of NOxand in N2O5NO3NO2air mixtures have been investigated at 296 ± 2 K and atmospheric pressure of air. Using a relative rate method, naphthalene‐d8was shown to react in N2O5NO3NO2air mixtures a factor of 1.22 ± 0.10 times faster than did naphthalene, with the 1‐ and 2‐nitronaphthalene‐d7product yields being similar to those of 1‐ and 2‐nitronaphthalene from naphthalene. From the measured PAH concentrations and the nitroarene product yields, formation yields of 2‐, 7‐, and 8‐nitrofluoranthene‐d9and 2‐ and 4‐nitropyrene of 0.03, 0.01, 0.003, 0.005, and 0.0006, respectively, were determined from the OH radical‐initiated reactions. Effective rate constants for the reactions of fluoranthene‐d10and pyrene with N2O5in N2O5;NO3NO2air mixtures of ca. 1.8 × 10−17cm3molecule−1s−1and ca. 5.6 × 10−17cm3molecule−1s−1, respectively, were derived. Formation yields of 2‐nitrofluoranthene‐d9and 4‐nitropyrene of ca. 0.24 and ca. 0.0006, respectively, were estimated for these reaction systems. 2‐Nitropyrene was also observed to be formed in these N2O5NO3NO2reactions, but was found to be a function of the NO2concentration and, therefore, would be a negligible product under ambient NO2concentrations. These product and kinetic dat

ISSN:0538-8066    

DOI:10.1002/kin.550220910

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550220901

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY