Reaction Progress Kinetic Analysis (RPKA) streamlines kinetic studies by exploiting the extensive data available from accurate in-situ monitoring of global reaction progress under “synthetically relevant” conditions, where the concentrations of two or more reactants are changing simultaneously – in fact, in the same manner that they are expected to change during practical synthesis. This contrasts with the classical approach to kinetics, which uses concentration ratios that are highly distorted, typically ca. 10 equivalents, in order to examine the order in each substrate’s concentration while holding the other constant. We have shown that the concentration dependences of two different substrates may be determined from far fewer reaction progress experiments compared to a classical kinetic approach. RPKA methodology is made straightforward for interpretation via the graphical manipulation of a mathematically determined minimum set of carefully designed experiments. One advantage of the RPKA approach is that vital kinetic information may be rapidly obtained and extracted even in earliest studies of a new reaction and may thus help inform the direction of both further reaction optimization and fundamental mechanistic investigation by other methods. The method requires little mathematical prowess and no specialized kinetic modeling techniques.
At its most basic level, the RPKA methodology consists of two sets of experiments, called “same excess” and “different excess” experiments. The “different excess” protocol provides information similar to that obtained in classical kinetic studies, that is, it gives the order in various reactant concentrations. The principal advantage of RPKA in this case is that this information is obtained from far fewer experiments than required for traditional kinetic analysis. However, it is in the “same excess” protocol that the RPKA methodology is most innovative, because here it provides not simply the same information more rapidly and with higher accuracy, but it extracts information about a working catalytic cycle that is difficult to obtain by any other means: “same excess” experiments help to differentiate a catalyst cycle that is operating at steady-state from one which is subject to temporal effects unrelated to the intrinsic reaction kinetics, such as catalyst activation or deactivation.
Additional kinetics resources.