Estimating reaction rate constants from a two-step reaction: a comparison between two-way and three-way methods

Abstract

In this paper, two different spectral datasets are used in order to estimate reaction rate constants using different algorithms. Dataset 1 consists of short-wavelength near-infrared (SW-NIR) spectra taken in time of the two-step epoxidation of 2,5-di-tert-butyl-1,4-benzoquinone using tert-butyl hydroperoxide and Triton B catalyst. This dataset showed moderate reproducibility. Dataset 2 consists of UV-VIS recorded spectra of the consecutive reaction of 3-chlorophenylhydrazonopropane dinitrile with 2-mercaptoethanol. This dataset showed good reproducibility. Two-way and three-way methods were used in order to estimate the reaction rate constants for both datasets. For the SW-NIR dataset the lowest standard deviations for the reaction rate constants were obtained with a two-way method. The lowest standard deviations for the reaction rate constant estimates for the UV-VIS dataset were obtained with a two-way method which uses spectral information that is known in advance. In this case the pure spectrum of two reacting absorbing species is known in advance and this information was used by the two-way method. For one two-way method and a few three-way methods which do not use spectral information that is known in advance, pure spectra of the reacting absorbing species of the UV-VIS dataset were estimated which showed excellent agreement with the recorded pure spectra. The pure spectra of the reacting absorbing species for the SW-NIR dataset were not estimated, because it was not possible to record the real pure spectra of these species. For both spectral datasets, quality assessment has been performed using a jackknife method. Copyright © 2000 John Wiley & Sons, Ltd.