Medium effects on the initial and the transition states upon the solvolysis of trans‐dichlorobis(N‐methyl‐ethylenediamine)cobalt(III) complex in water‐mixed solvents

Abstract

The kinetics of solvolysis of trans-dichlorobis(N-methylethylenediamine)cobalt(III)complex have been investigated in aqua-organic solvent media (0-60% (v/v) cosolvent) at 25 ≤ t • C ≤ 60, using n-propanol and tert-butyl alcohol as cosolvents. The first-order rate constant increased nonlinearly with the reciprocal of the dielectric constant D s −1 , and x org , reflecting the individuality of the cosolvents and thereby suggesting that the relative stabilities of the transition state and initial state were governed by the preferential solvation effect. The thermodynamic parameters ( H = and S = ) were sensitive to the structural changes in the bulk solvent phase.

Kinetics of Malachite Green Fading in Water‐ethanol‐1‐propanol Ternary Mixtures

“…The failure of the simple electrostatic interpretation shows the importance of hydrogen bonding and other nonelectrostatic medium effects in controlling the reactivity of the substrates. 33,35 In such cases, the differential solvation of the initial and transition states is the controlling factor for changes in the rate constant with the solvent composition. In SESMORTAC model, variation in mechanism is followed through the study of changes in microenvironment (or solvent cage) of the activated complex.…”

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.…”

“…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. The failure of the simple electrostatic interpretation shows the importance of hydrogen bonding and other nonelectrostatic medium effects in controlling the reactivity of the substrates 33,35. In such cases, the differential solvation of the initial and transition states is the controlling factor for changes in the rate constant with the solvent composition.…”

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.…”

“…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. The failure of the simple electrostatic interpretation shows the importance of hydrogen bonding and other nonelectrostatic medium effects in controlling the reactivity of the substrates 40,42. In such cases, the differential solvation of the initial and transition states is the controlling factor for changes in the rate constant with the solvent composition.…”