Chemical Systems Involving Two Competitive Self-Catalytic Reactions

Abstract

Self-catalytic reactions are chemical phenomena, in which a product catalyzes the reactions of substrates further to yield products. A significant amplification of product concentration occurs during the reactions in a dilute solution, which exhibit notable properties such as sigmoidal kinetics, seeding effects, and thermal hysteresis. Chemical systems involving two competitive self-catalytic reactions can be considered, in which the competitive formation of two products occurs, which is affected by environmental changes, subtle perturbations, and fluctuations, and notable chemical phenomena appear such as formation of different structures in response to slow/fast temperature changes, chiral symmetry breaking, shortcut in reaction time, homogeneous–heterogeneous transitions, and mechanical responses. Studies on such chemical systems provide understanding on biological systems and can also be extended to the development of novel functional materials.

Figure-eight thermal hysteresis of aminomethylenehelicene oligomers with terminal C16 alkyl groups during hetero-double-helix formation

“…Formation of random-coils 2A and hetero-double-helix B by (P)-1-C 16 /(M)-2 was determined in uorobenzene (0.5 mM) to be analogous to that with the (P)-1 and (M)-2 system. [32][33][34] A solution of (P)-1-C 16 /(M)-2 was heated to 70 C, and the CD spectra show a very weak Cotton effect of 2A ( Fig. 2a).…”

“…We have been studying thermal hysteresis in noncovalent chemical reactions of molecules dispersed in solution using helicene oligomers, and such a phenomenon was not previously observed. [32][33][34] When the rate was increased to 4.0 and 5.0 K min À1 , clockwise thermal hysteresis loops were obtained in the positive D3 domain between 0 and +62 cm À1 M À1 . Figure-eight thermal hysteresis appeared at intermediate rates of 1.5 and 2.5 K min À1 in the intermediate state of the counterclockwise and clockwise thermal hystereses.…”

“…A chemical reaction is described by the concepts of quantum and statistical mechanics. [32][33][34] In quantum mechanics, the structural changes of molecules and their relative thermodynamic stability involving diverse microscopic pathways, called microscopic mechanisms, are analyzed. In statistical mechanics, the ux or number of molecules that visit the pathways, called macroscopic mechanisms, is analyzed.…”

“…We have been studying the thermal hysteresis of noncovalent chemical reactions considering both microscopic and macroscopic mechanisms. [32][33][34] We have reported that thermal hysteresis can appear in reversible noncovalent chemical reactions of molecules dispersed in solution, which involve different macroscopic mechanisms during cooling and heating. This phenomenon is experimentally shown using different cooling and heating curves in proles, in which cooling and heating as the input provide substrate/product properties and concentrations as the output.…”

Speeding up Viedma Deracemization through Water‐catalyzed and Reactant Self‐catalyzed Racemization

“…Because product/ catalyst needs to be produced first, before it can exert its catalytic activity, a sigmoidal reaction rate profile with an initiation phase is the consequence. [33] The reverse of an autocatalytic step is trivially reactant-catalyzed, of course. Hence, to avoid confusion, we limit the discussion here to spontaneous (i. e. exergonic) processes.…”