Influence of solvent structure on the aquation of K‐chloro(diethylenetriamine)(ethylenediamine) cobalt(III) ion in water and mixed aqueous solvents

Abstract

The aquation of K-[Co(dien)(en)Cl] 2+ was followed spectrophotometrically within the temperature range (40-60 • C) in water, water-isopropyl alcohol, and water-tert-butyl alcohol media of varying solvent composition up to 50 and 60 vol% of the organic solvent component respectively. The nonlinear plot of log k vs. D −1 s was attributed to the differential solvation of the initial and transition states. The variation of H = , S = , and G = with the mole fraction of the organic component was analyzed and discussed. The isokinetic temperatures were found to be 330 and 317 K for water-isopropyl alcohol and water-tert-butly alcohol mixtures respectively, indicating that the aquation reaction is entropy controlled. The application of free energy cycle at 25 • C for the aquation reaction in both co-solvents suggests that the transition state is more stable than the initial one.

Effect of solvent and structure on the kinetics and mechanism of the aquation of bromopentaamine cobalt(III) complex in binary aqueous mixtures

“…The kinetics of aquation of cobalt(III) complexes in various water‐organic co‐solvents have been the subject of several studies in our laboratories 1–5. In homogeneous solutions, a solvent molecule around a solute molecule may take a conformation or a structure different from that in the bulk solution because of differences in solvent–solvent and solute–solvent interactions.…”

Kinetics of malachite green fading in water–ethanol–2‐propanol ternary mixtures

“…Data of Tables I–V were analyzed by the SESMORTAC model. In the SESMORTAC model 16, a range of solvent composition in which the equation of logarithm of the reaction rate constant, log k , versus a reciprocal of dielectric constant of the solution, D −1 , is linear 27–34, is called a “zone” and a solvent composition in which a zone finishes and another zone starts, is called “ m echanism c hange point” (or abbreviated as the mc point). Considering a mechanism on the basis of point charge on a dielectric continuum suggests that the plots of log k against D −1 should be linear.…”

Kinetics of malachite green fading in alcohol–water binary mixtures

“…Data of Tables I–VII were analyzed by using the SESMORTAC model. In the SESMORTAC model 16, a range of solvent composition in which the equation of logarithm of reaction rate constant, log k , versus reciprocal of the dielectric constant of the solution, D −1 , is linear 34–41, is called a “zone” and a solvent composition in which a zone finishes and another zone starts, which is called “ m echanism c hange point” (abbreviated as mc point). Consideration of a mechanism on the basis of point charge on a dielectric continuum suggests that the plots of log k against D −1 should be linear.…”