Kinetic Measurements

Abstract

Abstract Magde, Douglas (University of California at San Diego). The goal of kinetic measurements, which determine the rate of chemical changes, is to determine the form of a rate law. This law relates rates to reactant concentrations and one or more rate constants which remain unchanged as long as thermodynamic conditions are fixed. Measurements may be made by mixing components and measuring concentration changes over time. Methods, including stopped‐flow and continuous flow mixing for millisecond times, have been introduced to study reactions too fast for manual approaches. Faster reactions require perturbation methods employing temperature, pressure (including sound), and electrical field strength. Flash photolysis, also a perturbation, uses lasers to measure chemical or physical changes taking place in less than \documentclass{article}\pagestyle{empty}\begin{document}${10^{-13}}$\end{document} s. Other perturbation methods can approach \documentclass{article}\pagestyle{empty}\begin{document}${10^{-9}}$\end{document} s. Besides direct measurements of changing concentrations, kinetic studies can exploit linewidth measurements in optical spectroscopy and magnetic resonance. All these measurements of macroscopic behavior are then interpreted at the microscopic, atomic level in terms of mechanisms. The combination of increasingly detailed, fast measurements of primary processes and sophisticated computer modeling is starting to generate rigorous atomic level descriptions of kinetic change. Vol. 14, pp. 1021–1044, 16 refs. to December 1993.