Linear Control of Temperature with Time—A New Approach to Reaction Kinetics


  • Dr. Erhard Koch

    Corresponding author
    1. Max-Planck-Institut für Strahlenchemie, Stiflstrasse 34—36, D-4330 Mülheim a. d. Ruhr 1 (Germany)
    • Max-Planck-Institut für Strahlenchemie, Stiflstrasse 34—36, D-4330 Mülheim a. d. Ruhr 1 (Germany)
    Search for more papers by this author


The temperature dependence of the rate of chemical reactions has been known for a long time; very often it is characterized by the Arrhenius plot. However, kinetic methods that take this phenomenon into account in one measurement in a planned manner have been applied to reactions in solution only in isolated examples-with the exception of the temperature jump method developed by Eigen et al. for fast reactions, based on a stepped temperature program. A mathematical analysis, however, reveals to the chemist that from the point of view of information theory the course of the reaction rate versus time under conditions of constantly increasing temperature is the measured signal which should lead to the most effective understanding of the reaction mechanism. Analysis of the measured peaks, which may overlap, allows the characterization of reactions either in the solid state or in solution by “mechanistic coordinates”, which extend the concept of reaction order. Their behavior allows further experiments to be planned, enabling elementary steps to be eliminated. Each reacting system can be characterized kinetically by one series of experiments using different starting concentrations for each reactant and additionally, using different heating rates. The experimental verification of these considerations can be seen in ca. 1400 DTA and UV experiments for ca. 120 different systems. Furthermore, the example of the oscillating Belousov-Zhabotinsky reaction shows that “fast” reactions frequently may also be recognized. A test for proposed reaction mechanisms is provided by integration programs which allow immediate comparison between experimental and theoretical signal curves.