Stopped-flow investigation

These results do not prove that the ester is an essential intermediate in aqueous solution even though it is present, but the result with the hindred triterpene is convincing In this case the esterification step, which is normally fast, has become rate-determining and the disappearance of the isotope effect must mean that C-H cleavage occurs after the formation of the ester and not independently of it. The generality of this result is apparent from the stopped-flow investigation of isopropanol oxidation ... 

D. Barth, C. Tondre, J. J. Delpuech, Stopped-flow investigations of the reaction kinetics of carbon dioxide with some primary and secondary alkanolamines in aqueous solution, Int.J. Chem. Kin., 1986, 28, 445-457. 

Breen et al. (1986) report the results of a stopped-flow investigation of metal ion exchange kinetics between Tb(III) and Ca(EDTA). The progress of the reaction was monitored by Tb(III) luminescence. These authors interpret the data to indicate that metal ion exchange occurs via acid-catalyzed dissociation of the Ca(EDTA) complex with rapid formation of the Tb(III)-EDTA complex, and through a parallel process involving a dinuclear intermediate. The acid-catalyzed dissociation pathway is the preferred mode. 

A stopped-flow investigation of the kinetics of the oxidative substitution of the [Co(NH3)sBr] + ion by CU, HOCI, and HOBr has appeared. In excess HOBr, a third-order rate law is observed ... 

Several kinetic studies of nucleophilic attack upon coordinated car-benes have appeared. Particularly revealing has been a stopped-flow investigation of the addition of PBu and P(OBu")3 to the carbene carbon in the chromium triad carbenes, [M(CO)sCR (OEt)] (M = Cr, Mo, or W R = Ph or Me) [equation (1)]. The forward rate constant, ki, is little... 

Figure 6.4 Data from temperature jump relaxation experiments (Halford, 1973) on the interaction of the l-4 linked riimer of M-acetyl-D lucosamine with lysozyme at pH 4.4 monitoring H release. The concentration scale corresponds to the sum of the equilibrium concentrations of enzyme and ligand, (a) shows that the concentration dependence of the reciprocal relaxation time reaches a limit of 240 s which is similar to the fluorescence data of Holler et al., 1969. (6) illustrates a mechanism proposed by Halford (1975) from his relaxation and stopped-flow investigation of fluorescence changes and proton release over a range of pH.

Mukai, K., Fukuda, K., Ishizu, K. and Kitamura, Y. (1987) Stopped-flow investigation of the reaction between vitamin E radical and vitamin C in solution. Biochem. Biophys. Res. Commun., 146 (1), 134-139. 

Unfortunately there have been no more recent investigations using fast kinetic methods such as stopped flow, by adding methanol or even methanol with some water to the ether solution obtained by the procedure of Muller and Haiss, so as to check whether an equilibrium mixture of nitrosoamine and diazohydroxide is formed. 

A stopped flow technique coupled with spectrophotometric analysis of the iron (II) complex formed has been used to investigate - the reactions of some organic complexes of iron(III) with the ion Fe ". The iron(III) was complexed with 1,10-phenanthroline, various substituted 1,10-phenanthrolines (5-methyl-, 5-nitro-, 5-chloro-, 5-phenyl-, 5,6-dimethyl-, 4,7-diphenyl-, and 3,4,7,8-tetramethyl-) and 2,2 -dipyridine, 4,4 -dimethyl-2,2 -dipyridine, and 2,2, 2"-tripyridine. The wavelengths used for the analysis lay in the region 500-552 m/i. 

Espenson has shown that the reaction of c/j-Co(en)2(N3)2 with takes place by an inner-sphere mechanism. This Co(III) complex was selected for investigation because it is particularly reactive towards and also the dissociation of monoazido vanadium(lll) is relatively slow. At low concentrations (2-20 X 10 M) the second-order rate coefficient is 32.9 l.mole . sec at 25 °C, [H ] = 0.10 M and [i = 1.0 M. At higher concentrations ( 0.1 M), using a stopped-flow apparatus, the kinetics are apparently first order at 520 mfi, a wavelength where shows negligible absorbance. The rate coefficient under... 

Beattie and Basolo have investigated the reactions of the substitution-inert octahedral complexes of Pt(IV) with tris(bipyridine)chromium(II). A rapidmixing, stopped-flow apparatus was made use of in the majority of experiments. 

The reaction between peroxysulphuric acid and thiocyanate ions was investigated by Smith and Wilson by a stopped-flow conductance method. Their results can be summarized as follows. If / and m are the numbers of moles of cyanate and sulphur dicyanide produced per mole of thiocyanate consumed, the overall stoichiometric equation is... 

Kane DJ, Fendler K, Grell E et al (1997) Stopped-flow kinetic investigations of conformational changes of pig kidney Na+,K+-ATPase. Biochemistry 36 13406-13420... 

Cormier M.J.,Prichard P.M., An investigation of the mechanism of the luminescent peroxidation of luminol by stopped flow techniques, J. Biol. Chem. 1968 243 4706-4714. 

An investigation of the kinetics of formation of the Li+ and Ca2+ complexes of cryptand 2.1.1 using stopped-flow calorimetry suggests that complexation occurs initially at one face of the cryptand such that the metal is only partially enclosed (to yield an exclusive complex). Then follows rearrangement of this species to yield the more stable product, containing the metal ion inside the cryptand (the inclusive product) (Liesegang, 1981). X-ray diffraction studies have indeed demonstrated that exclusive complexes are able to be isolated for systems in which the metal is too large to readily occupy the cryptand cavity (Lincoln et al., 1986). 

Ni2+ was very popular in the early days of the investigation of mechanisms of complex formation, since the time-scale for its reactions with simple ligands was so convenient for the then recently developed stopped-flow technique. However, interest has now moved on to other first-row cations, especially to Cu2+. A review of the kinetics and mechanisms of formation of tetraazamacrocyclic complexes concentrates on Ni2+ and Cu2+, and their reactions with cyclam and similar ligands (267). The tetra(4 -sulfonatophenyl)porphyrin complexes of Ni2+ and of Cu2+ react immeasurably slowly with cyanide, but their IV-methyl derivatives do react, albeit extremely slowly. The relevant time scales are hours for removal of Ni2+, months for the removal of Cu2+, by 10-4 M cyanide at pH 7.4 (268). 

A detailed stopped-flow kinetics investigation (85) of this reaction (Por = TmTP and OEP) demonstrated that the mechanism occurs in two stages. The first was quite fast and was suppressed by the presence of excess CO and other coordinating ligands. Time resolved infrared... 

The systems that we investigated in collaboration with others involved intermolecular and intramolecular electron-transfer reactions between ruthenium complexes and cytochrome c. We also studied a series of intermolecular reactions between chelated cobalt complexes and cytochrome c. A variety of high-pressure experimental techniques, including stopped-flow, flash-photolysis, pulse-radiolysis, and voltammetry, were employed in these investigations. As the following presentation shows, a remarkably good agreement was found between the volume data obtained with the aid of these different techniques, which clearly demonstrates the complementarity of these methods for the study of electron-transfer processes. 

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