Mean centering of ratio spectra as a new method for determination of rate constants of consecutive reactions

Mean centering of ratio spectra is applied to resolve two-way kinetic-spectral data and acquire the rate constants and the spectrum of intermediate component. The proposed method can be applied for two-step consecutive reactions. The method is based on the mean centering of ratio spectra in order to obtain kinetic profile of intermediate component. Rate constants can be obtained using computational fitting. Given the kinetic parameters, the absorption spectrum of intermediate can be obtained through least squares regression. The proposed method can be applied to the reaction systems that reactant, intermediate or final product does not absorb in the investigation wavelength region. Also for very slow one-step reactions that pure spectrum for product is not available or overlaps completely with reactant spectrum, the proposed method can be used to resolve kinetic profile and consequently the pure spectrum of product. The applicability of the method has been evaluated by using model data. Alkaline hydrolysis of dimethyl phthalate as a real system was also studied by the proposed method. (C) 2007 Elsevier B.V. All rights reserved.