Chapter 3 - Rate laws

Abstract

The overall kinetics of a chemical reaction depend on thermodynamic properties, transport properties, and intrinsic kinetics. All chemistry students learn that kinetics depend on concentrations and on temperature. Clearly, the kinetics of a chemical reaction also depend on the molecular characteristics of the reactants and catalysts. Indeed much of basic chemistry concerns differences in reactivity for molecules with different steric characteristics, different electrostatic characteristics, different frontier orbital characteristics, different acidities, etc. More subtle factors can also influence reactivity. For example, isotope effects can be approximately predicted and used to test hypotheses about rate limiting steps. The kinetics of reactions in solution also depend on solvent properties like viscosity, ionic strength, and hydrogen bonding propensity. The kinetics of catalytic reactions often depend on mass transfer and heat transfer limitations. The kinetics of gas phase reactions depend on vibrational coupling within molecules and sometimes on the partial pressure of inert collision partners. Some processes like electron transfer and protein folding can be driven by external potentials or forces which influence their kinetics. Each of these effects has been mechanistically informative and integral to the development of modern theories of kinetics.