. Can. J. Chem. 69, 157 (1991). In models of the kinetics of chemical reactions in solution the solvent is commonly assumed to be a uniform continuum. An example is the Smoluchowski-Debye-Stokes-Einstein equation for the rate constant k2 of a bimolecular reaction between charged or polar species:where K is the probability that a reactant encounter pair will react, R is the gas constant, T is the temperature, f is a factor that reflects the effect of electrostatic interaction between the reactants on their probability of attaining the closeness of approach r, at which reaction occurs, q is the solvent viscosity, and rd is the effective radius of the reactant entities for mutual diffusion. The equation is useful in evaluating effects of bulk fluid properties on reaction rates. Residual effects are attributed to more specific solvent behaviour.Rate constants kZ, activation energies E2, and pre-exponential factors A2 of reactions of solvated electrons e; with H: , Ag:, CU?, and A17 ions vary with the composition of 1-propanol/water and 2-propanol/water mixed solvents. Plots of k2q/fT against solvent composition are nonlinear and change with the solvent pair and with reactant pair. Measured molar conductivities Ao(H:, ClO,,), Ao(Ag:, ClOc,), Ao(cu?, 2C10<,), and Ao(~13:, 3C104,) indicate that the values of rd for the mutual diffusion of the cations and anions have a minimum near 90 mol% water, and that the values in pure propanol-1 or -2 (150-190 pm) are larger than those in pure water solvent (26 pm for H: ,70 pm for the metal ions). The liquid structure influences both the rate of diffusion and the probability of reaction of a reactant encounter pair.Key words: alcohol/water mixed solvents, positive ions, reaction kinetics, solvated electron, solvent effects. dans laquelle K est la probabilitk qu'une paire de rkactifs qui se rencontrent puissent reagir, R est la constante des gaz, Test la temperature, f est un facteur qui est le reflet de l'interaction ~lectrostati~uk entre les reactifs sur la probabilitk qu'ils ont de s'approcherjusqu'i une valeur de r, i laquelle il se produit une rkaction, q est la viscositk du solvant et rd est le rayon effectif des entites qui reagissent pour la diffusion mutuelle. L'kquation est utile pour kvaluer les effets globaux des propriktks des fluides sur les vitesses de reactions. Les effets residuels sont attribues i un comportement plus spkcifique du solvant.Les constantes de vitesse kZ, les knergies d'activation EZ et les facteurs prk-exponentiels A2 des reactions des ions solvatks e; avec les ions H:, Ag:, CU? et ~1 7 varient avec la composition des solvants mixtes 1-propanol/eau et 2-propanol/eau. Les courbes de k2q/fT en fonction des compositions de solvants ne sont pas linkaires et elles varient avec la paire de solvant et la paire de reactif. Les conductivitCs molaires mesurkes Ao(H:, ClO:,,), Ao(Ag:, ClO:,,), Ao(cu;+, 2C10;,,) et Ao(A1:+, 3C10cS) indiquent que les valeurs de rd pour la diffusion mutuelle des cations et des anions passent par un minimum prks de 90 mol% d'eau ...

The Smoluchowski-Debye-Stokes-Einstein equation for the rate constant kz of a bimolecular reaction between charged or polar species was used to evaluate effects of bulk solvent properties on reaction rates of solvated electrons with NOT,,, H: , TI:, Cu:' , and AI:' in 2-butanol/water mixed solvents. To explain detailed effects it was necessary to consider more specific behavior of the solvent. Rate constants k 2 , activation energies E2, and pre-exponential factors Az of these reactions vary with the composition of 2-butanol/water mixtures. The values of E2 were in general similar to activation energies of ionic conductance EAo of the solutions, except for much higher values of E2 of (e; + NOT,,) in alcohol-rich solvents and of (e; + ~1:') in pure water solvent.The solvent apparently participates chemically in the NOT, reaction, and the ~1:' reaction is multistep. Rate constant and conductance measurements of thallium acetate solutions in 2-butanol containing zero and 10 mol% water were complicated by the formation of ion clusters larger than pairs.