0000000000030897
AUTHOR
Francisco Pérez Pla
THE KINETICS AND MECHANISM OF THE REACTION OF ONIUM CYCLOPENTADIENYLIDES WITH TETRAHALO-p-BENZOQUINONES
Abstract The reaction of triphenylphosphonium cyclopentadienylide (1) with halogen-substituted p-benzoquinones (4) is shown to give a new class of dipolar (zwitterionic) dyes (5) containing phosphorus. The general structure of these molecules has been investigated by a combination of mass spectrometry and multinuclear (7H, 13C and 31P) nmr using the specialist techniques of DEFT spectroscopy, homonuclear (COSY) and heteronuclear 2-D nmr. In addition, stopped-flow (uv/visible) techniques have been used to study the kinetics of the reactions and hence demonstrate that the rate-limiting step is nucleophilic addition of the ylid nucleophile to the quinone, followed by a rapid loss of halide ion…
Reactivity of Neutral Mo(S2C6H4)3 in Aqueous Media: an Alternative Functional Model of Sulfite Oxidase.
The kinetics of the reaction of neutral [Mo(S2C6H4)3] with hydrogen sulfite to produce the anionic Mo(V) complex, [Mo(S2C6H4)3]-, and sulfate have been investigated. It has been shown that [Mo(S2C6H4)3] acts as the electron-proton sink in the oxygenation reaction of HSO3(-) by water. Reaction rates, monitored by UV/vis stopped-flow spectrometry, were studied in THF/water media as a function of the concentration of HSO3(-) and molybdenum complex, pH, ionic strength, and temperature. The reaction exhibits pH-dependent HSO3(-) saturation kinetics, and it is first-order in complex concentration. The kinetic data and MS-ESI spectra are consistent with the formation of [Mo O(S2C6H4)2(S2C6H5)]- (1…
On the integration of kinetic models using a high-order taylor series method
A general equation to derive kinetic models up to any order is given. This equation greatly facilitates the application of the Taylor series method to the integration of kinetic models up to very high orders. When dealing with non-stiff models, computing time is always reduced by increasing the integration order, at least up to the 20th order. When the model is stiff, the integration order should be optimized; however, a twelfth order is recommended to integrate weakly stiff models. The use of an algorithm which permits the immediate calculation of the integration step size required to maintain a given accuracy leads to further reductions in computing time. When implemented as recommended h…