Showing papers in "Progress in Reaction Kinetics and Mechanism in 2005"
TL;DR: A critical overview of phenomenological thermodynamic approaches to reaction rate equations of the type based on the law of mass-action is given in this paper, where treatments based on classical equilibria are discussed.
Abstract: A critical overview is given of phenomenological thermodynamic approaches to reaction rate equations of the type based on the law of mass-action. The review covers treatments based on classical equ...
46 citations
TL;DR: A review of both mechanistic and practical investigations in relation to catalysis and environmental applicat... as mentioned in this paper is presented in Section 2.1, Section 3.1.1].
Abstract: Many reactions that occur on solid surfaces are mediated by free radicals. A review is presented of both mechanistic and practical investigations in relation to catalysis and environmental applicat...
40 citations
TL;DR: In this article, the second order fits were drawn by the software associated with a Cary UV spectrophotometer model Bio-300 at appropriate wavelength, and the values of the second-order rate constant (k2) were calculated using standard equations within the program.
Abstract: Kinetic studies were made of the reactions between triphenylphosphine, dialkyl acetylenedicarboxylates in the presence of SH-acids, such as 2-thiazoline-2-thiol or 2-mercaptobenzoxazole. To determine the kinetic parameters of the reactions, they were monitored by UV spectrophotometery. The second order fits were drawn by the software associated with a Cary UV spectrophotometer model Bio-300 at appropriate wavelength. The values of the second order rate constant (k2) were calculated using standard equations within the program. Within the temperature range studied, the dependence of the second order rate constant (ln k2) on reciprocal temperature was in agreement with the Arrhenius equation, enabling calculation of the activation energies of all reactions. Furthermore, useful information was obtained from studies of the effect of solvent, structure of reactants (different alkyl groups within the dialkyl acetylenedicarboxylates and SH-acids) and also concentration of reactants on the rate of reactions.
19 citations
TL;DR: The kinetics and mechanism of CrVI oxidation of D-glucose in the presence and absence of 1,10-phenanthroline (phen) in aqueous acid media have been studied under the conditions, [sugar]T ≥ [CrVI]T at different temperatures.
Abstract: The kinetics and mechanism of CrVI oxidation of D-glucose in the presence and absence of 1,10-phenanthroline (phen) in aqueous acid media have been studied under the conditions, [sugar]T ≥ [CrVI]T at different temperatures. The monomeric species of CrVI has been found to be kinetically active in the absence of phen whereas in the phen-catalysed path, the CrVI - phen complexes have been found to be the active oxidants. Both the paths show a first order dependence on [sugar]T and [CrVI]T. The uncatalysed path shows a second order dependence on [H+], while the catalysed path shows a first order dependence on [H+]. The phen-catalysed path is first-order in [phen]T. These observations remain unaltered in the presence of externally added surfactants. CPC inhibits both pathways while SDS catalyses the reactions.
6 citations
TL;DR: The CrVI oxidation of a mixture of DMSO and oxalic acid in aqueous acid media occurs much faster than that of either of the two substrates alone.
Abstract: The CrVI oxidation of a mixture of dimethyl sulfoxide (DMSO) and oxalic acid (OXH2) in aqueous acid media occurs much faster than that of either of the two substrates alone (DMSO reacts extremely s...
4 citations
TL;DR: In this paper, the authors propose two sources of methane replenishment, i.e., recycling of the primordial reserve trapped in Titan's interior and reconversion of non-saturated final products of the atmospheric photochemical process, which is the minor constituent in the global methane balance.
Abstract: Methane CH4 is the only highly reactive and short-lived background component in Titan's atmosphere, so its overall reserve predetermines both features and duration of atmospheric chemical activity. Current methane atmospheric abundance is provided by its global circulation. There are two sources of methane replenishment, i.e. recycling of the primordial reserve trapped in Titan's interior and reconversion of non-saturated final products of the atmospheric photochemical process, reconversion being the minor constituent in the global methane balance. The total bulk of primordial methane gas hydrate depends on the packing index (cage-filling efficiency) α, the latter being limited to 7.2 × 10−4< α < 5 × 10−2 {kg CH4/kg clathrate}. The specification of α seems to be one of the most relevant problems of the experimental modelling of Titan's chemistry. The total number of methane renewal cycles so far equals Np ∼ 200.
2 citations
TL;DR: The kinetics and mechanism of action of the most intensively studied mammalian peroxidases, myeloperoxidase and prostaglandin H synthase are critically reviewed and evidence against currently favored mechanisms is presented.
Abstract: The kinetics and mechanism of action of the most intensively studied mammalian peroxidases, myeloperoxidase and prostaglandin H synthase are critically reviewed. Evidence against currently favored mechanisms is presented. It is shown that myeloperoxidase has a strong defence mechanism against free hypochlorous acid, commonly thought to be its principal product in its bactericidal activity. Rather, after its two-electron oxidation of chloride ion, myeloperoxidase rapidly converts it into an enzyme-bound chlorinating intermediate, most likely a chlorinated distal imidazole ring. This species chlorinates taurine which may either be a transfer agent of Cl+ to other species or may act directly in attack on invading microorganisms. The currently favored mechanism of action of prostaglandin H synthase-1 is a branching chain mechanism in which Compound I is converted into a species containing a tyrosyl radical on the opposite side of the enzyme. Once the tyrosyl radical is formed it converts arachidonic acid into a peroxide in a cyclooxygenase reaction, independent of the peroxidase activity. This mechanism cannot explain the enhancing effect of small free radical scavengers, nor the fact that peroxidase activity continues unabated while the cyclooxygenase reaction is proceeding, nor the 2: 1 ratio of small free radical scavenger to arachidonic acid consumption. A tightly coupling of peroxidase and cycloxygenase reactions appears to be the steady state mechanism, and the branching chain mechanism, if it occurs, is confined to a burst transient state phase.
2 citations
TL;DR: In this article, a correlation analysis of the rate of the oxidation of thirty-five sulfides was performed in terms of various single and multiparametric equations, and the best correlation was obtained with Charton's LDR and LDRS equations.
Abstract: The oxidation of organic sulfides by [bis(trifluoroacetoxy)iodo]benzene (TFAIB), to the corresponding sulfoxides, is first order with respect to TFAIB, hydrogen-ions, and the sulfide. The correlation analyses of the rate of the oxidation of thirty-five sulfides were performed in terms of various single and multiparametric equations. For the aryl methyl sulfides, the best correlation is obtained with Charton's LDR and LDRS equations. The oxidation of alkyl phenyl sulfides exhibited a very good correlation in terms of the Pavelich-Taft equation. The polar regression coefficients are negative. A mechanism involving formation of a sulfonium-cation intermediate in the slow step has been proposed.
1 citations
TL;DR: In this paper, the reaction rates of atomic carbon in its electronic ground state, C[2p2 (3PJ), with a range of large sulfur-containing molecules have been investigated using time-resolved atomic spectroscopy in the vacuum ultraviolet following pulsed irradiation.
Abstract: Reaction rates of atomic carbon in its electronic ground state, C[2p2 (3PJ)], with a range of large sulfur-containing molecules have been investigated using time-resolved atomic spectroscopy in the vacuum ultraviolet following pulsed irradiation. Absolute rate data for the collisional removal at 300 K of C(23PJ) by the gases 1-propanethiol, 1-butanethiol, 1-pentanethiol, 2-propanethiol, 2-methyl-1-propanethiol, 2-methyl-2-propanethiol and dimethyl sulfide are reported. All processes proceed at rates of the order of the collision numbers, supporting an overall mechanism of C-atom insertion into the S–H bond following initial addition, which is energetically favourable, a mechanism demonstrated analogously hitherto with H2S and where H-atom abstraction would also be endothermic.
1 citations