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. Can. J. Chem. 65,2441Chem. 65, (1987. Viscosity and density of 27 binary mixtures of sec-, iso-, and tert-butanol with water were measured at 273 5 T/K 5 353 and the results summarized using polynomials. At fixed T the density depended strongly but monotonically on mole fraction. The excess volume vE was large and negative. In H20/tert-butanol as T increased vE increased, while in H20/sec-or iso-butanol vE decreased with increasing T. The excess viscosity was large and positive in all cases.P. CHANDANI SENANAYAKE, NORMAN GEE et GORDON R. FREEMAN. Can. J. Chem. 65,2441. Operant A des temperatures allant de 273 A 353 K, on a mesurt les viscosites et les densitts de 27 melanges binaires d'eau avec les sec-, iso-et tert-butanols et on a rtsum6 les rtsultats en utilisant des polynbmes. A temperature constante, la densitt depend beaucoup de la fraction molaire, mais d'une fagon monotone. La valeur du volume en excks vE est importante et negative. Dans le melange H20/tert-butanol, la valeur de vE augmente avec une augmentation de la temperature; par ailleurs, dans les mClanges H20/sec-ou iso-butanol, les valeurs de vE diminuent avec une augmentation de la temperature. Dans tous les cas, la valeur de la viscosite en excks est importante et positive.[Traduit par la revue]

The reactivity of solvated electrons (ef) with scavenger (S) in Zerf-butyl alcohol/water mixtures is greatly affected by the solvent structure. The variation of the rate constant k2 with solvent composition displays four zones. The two water-rich zones are characterized by a large change in solvent viscosity and a small change in optical absorption energy £r of the es'; here k2 for all scavengers correlates inversely with . In the two alcohol-rich zones the change of is small and that of ET is large; here k2 for efficient scavengers changes slightly in a complex manner with solvent composition, while for the inefficient scavengers k2 correlates inversely with £r. Similar zone behavior occurs in the Arrhenius activation energy E2 and entropy of activation AS2*, as well as in £, for the solvent viscosity; £2 is related to solvent rearrangement about the reaction site.

The nearly diffusion controlled reaction rate constants k2 of solvated electrons with efficient electron capturers in butanol/water mixtures are examined according to the Smoluchowski, Debye, and trap-depth models. The k2 values depend on the diffusion rates of the reactants and the solvation energies of the electrons. Both these factors are affected by the rigidity of the alkyl group on the alcohol. Increased rigidity decreases the diffusion rate, which tends to decrease k2, and decreases the electron solvation energy, which tends to increase k2. Rate constants of efficient electron capturing solutes are dominated by the former, those of inefficient capturers by the latter. The free energy of activation ΔG‡13 for electron capture by an inefficient electron scavenger (solute) is empirically related to Er/ f(μ), where Er is a representative optical absorption energy of the solvated electrons (related to the solvation energy) and f(μ) is a function of the dipole moment of the scavenger. It is also related to the polarizability of the solvent molecules. Capture by an inefficient solute has a large negative entropy of activation attributed to solvent rearrangement about the reaction site.

The nearly diffusion-controlled rate constants k2 of solvated electrons with neutral polar scavengers or charged scavengers in terz-butyl alcohol/water mixtures are analyzed according to the Debye model. The differences of k2 between (es" + polar solute) and (es~+ charged solute) arise because of differences in the effect of static dielectric permittivity c on the reaction radii R and on the effective diffusion radii r. In alcohol-rich mixtures where the dielectric constants are lower and dielectric relaxation times are greater, larger r values result. In the water-rich mixtures the electrons are solvated in water-rich microphases, giving rise to similar r values in spite of large changes in c.