Kinetic Studies of Solute-Solvent Interactions in the Solvolysis of Trans- [Co (4-Teri-Butylpyri Dine)₄C1₂)Clo₄ in Organic-Aqueous Mixtures

Abstract

The kinetics of solvolysis of trans-[Co(L) 4 Cl 2 ]ClO 4 where (L ¼ 4-tert-butylpyridine) were followed spectrophotometrically in water -dioxane and waterdimethylsulfoxide media (0 -60% v=v) over the temperature range (40 -55 C). Non-linear plots were found for the logarithm of the rate constant of the first-order reaction versus the reciprocal of the relative permittivity, e r , of the mixed solvent. This behaviour can be attributed to the differential solvation of the initial and transition states of the complex. The enthalpies and entropies of activation showed compensating extrema with the mole fraction of solvent, leading to a small variation in the free energy of activation. By applying a free-energy cycle, it was found that the difference between the values of the free energy of transfer of the cations in the transition and initial states were negative, indicating that the cation in the transition state is more solvated than that in the initial state.

Analyses of reaction rate data for the simple hydrolysis of acetic anhydride in the acetonitrile/water and acetone/water cosolvent systems using recently developed thermodynamic rate equations

“…Contributions from T Δ S ‡ that are on the order of 60% or higher generally correlate with , in agreement with the results here. Reaction systems having contributions somewhat lower than 60% often correlate with , indicating that for such reactions either the reactive components are all randomly solvated, or the terms in Equation largely cancel. Given the results in this work, it is likely that the kinetic behavior for acetic anhydride hydrolysis would show little variation for almost any aqueous cosolvent system.…”

“…Although quantitative results using standard methods, such as the Kirkwood-Buff integrals, 26,27 cannot generally be used to analyze transition states, some inferences can be made using Equation (33). The expanded version of Equation (32) for the reaction systems in this work with n = 1 is…”

Detailed thermodynamic analysis of the activation parameters for the simple hydrolysis of acetic anhydride in the acetonitrile/water cosolvent system

“…Using eqn (27), (28), (39), and (42) Eqn (43) and (44) apply in the ranges 0.790 # X water # 1.000 and 15.0 # T # 55.0 C.…”

“…[39][40][41] The contribution from the activation entropies for metal complex hydrolyses is much lower than for simple acetic anhydride hydrolysis. Metal calculate these terms has been estimated from the following expression:…”

Electrochemical and computational analysis of solvent effects on the kinetics of reaction of nitrite ion with o-quinone

“…According to Eqn (1), in order to investigate the effect of solute-solvent electrostatic interaction on reaction rate, log k obs (relative) is plotted versus 1/ε ( Figure 7) [19]. Figure 7 shows that log k obs varies linearly with the reciprocal of the relative permittivity.…”