What is special about autocatalysis?

Abstract

The notion of autocatalysis has been introduced by the German chemist Wilhelm Ostwald [ 1 ] for the characterization of reactions that show an acceleration of the rate as a function of time. Autocatalytic reactions, however, were never popular in conventional chemistry and chemical technology mainly for two reasons: (1) autocatalysis gives rise to positive feedback, which is difficult to control and to handle in large reactors, and (2) autocatalytic systems may show complex dynamical phenomena such as bistability, oscillations, deterministic chaos, and spontaneous formation of spatial patterns or waves, which are not desirable in chemical production. The whole collection of these phenomena has been called nonlinear chemical dynamics by Irving Epstein and others [ 2 , 3 ]. In the second half of the twentieth century, however, complex dynamics and its embedding in thermodynamics have been shifted into the center of physical interest. Experimental chemical reaction systems showing nonlinear phenomena, in particular oscillations and spatial pattern formation, were investigated [ 4 , 5 ]. Autocatalysis was recognized as a basis for self-organization and has been extensively discussed in the context of models for the origin of life [ 6 ]. Oscillations in chemical reactions have been reported earlier [ 7 ] but these were singular studies and they took place in heterogeneous media. Beginning around 1960 with the studies of Boris Belousov and Anatol Zhabotinskii on a chemical reaction that exhibits oscillations in homogeneous solution, investigations on chemical self-organization became popular. Since then, a true wealth of experimental works and many theoretical studies on nonlinear chemical dynamics were performed [ 3 ].