Determination of rate constants in second-order kinetics using UV-visible spectroscopy

A general method for estimating reaction rate constants of chemical reactions using ultraviolet-visible (UV-vis) spectroscopy is presented. The only requirement is that some of the chemical components involved be spectroscopically active. The method uses the combination of spectroscopic measurements and techniques from numerical mathematics and chemometrics. Therefore, the method can be used in cases where a large spectral overlap of the individual reacting absorbing species is present. No knowledge about molar absorbances of individual reacting absorbing species is required for quantification. The reaction rate constants and the individual spectra of the reacting absorbing species of the two-step consecutive reaction of 3-chlorophenylhydrazonopropane dinitrile,vith 2-mercaptoethanol were estimated simultaneously from UV-vis recorded spectra in time. The results obtained were excellent.