Thermodynamics of Intrinsic Reaction Coordinate (IRC) Chemical Reaction Pathways

We address the scientific "time" concept in the context of more general relaxation processes toward the <i>Wärmetod</i> of thermodynamic equilibrium. More specifically, we sketch a construction of a conceptual ladder of chemical reaction steps that can rigorously bridge a description from the microscopic domain of molecular quantum chemistry to the macroscopic materials domain of Gibbsian thermodynamics. This conceptual reformulation follows the pioneering work of Kenichi Fukui (Nobel 1981) in rigorously formulating the <i>intrinsic reaction coordinate</i> (IRC) pathway for controlled description of non-equilibrium passages between reactant and product equilibrium states of an overall material transformation. Elementary <i>chemical reaction steps</i> are thereby identified as the logical building-blocks of an integrated mathematical framework that seamlessly spans the gulf between classical (pre-1925) and quantal (post-1925) scientific conceptions and encompasses both static and dynamic aspects of material change. All modern chemical reaction rate studies build on the apparent infallibility of quantum-chemical solutions of Schrödinger's wave equation and its Dirac-type relativistic corrections. This infallibility may now be properly accepted as an added"inductive law" of Gibbsian chemical thermodynamics, the only component of 19th-century physics that passed <i>intact</i> through the revolutionary quantum upheavals of 1925.