Spectroscopic–kinetic analysis of first and second order reactions on the basis of multidimensional absorbance (A) diagrams

Abstract

The absorbance (A), absorbance difference (AD) and absorbance difference quotient (ADQ) diagrams are called Mauser diagrams. Typically, these diagrams represent two-dimensional plots. The so-called Mauser space is multidimensional (n2). The axes of this space are established by the absorbances or absorbance differences of n wavelengths. A reaction system that consists only of one linearly independent reaction step (s = 1) leads to a straight line in Mauser space. This line is obtained independent of the reaction order of the system. A one-dimensional coordinate axis can be established which is orientated in the direction of the straight line lying in the Mauser space (n>s). The distances of the individual measured points with regard to the origin of the (one-dimensional) coordinate system can be evaluated kinetically. The procedure is demonstrated using reactions of first and second order (s = 1; n = 4 and 6). A reaction system described by two linearly independent steps (s = 2) leads to a curve in the Mauser space which lies on a plane. A two-dimensional coordinate system can be introduced which lies in this plane. The coordinates of the Mauser curve with regard to the established (two-dimensional) coordinate system can be evaluated kinetically. The procedure is shown by evaluating reactions of first and second order (s = 2; n = 3 and 4). The advantages of geometric analysis of Mauser space are discussed.