Effects of Electronegative Substituents of Anions on Ion-Pair Formation. 1. Temperature Dependence of the Conductivity of Lithium Fluoroacetate and Alkali-Metal Acetate Solutions in Dimethyl Sulfoxide

Abstract

The effect of electron-withdrawing substituents on ion−ion interactions is exemplified by conductivity studies on dimethyl sulfoxide solutions of lithium acetate and fluoroacetates. Association constants decrease upon increasing fluorine substitution by a factor of 50. They are correlated with mean oxygen charges calculated with the help of semiempirical quantum mechanical methods. The distance parameters from such calculations prove to be good estimates for the liquid state. Non-Coulombic contributions of the CH3COO- ion to the ion−ion interactions show stronger competition with solvent molecules in the solvation shell of the Li+ ion than the CF3COO- ion, which is a weak ligand in comparison to the dimethyl sulfoxide molecule.

Thermochemical studies on the lanthanoid complexes of trifluoroacetic acid

“…This might be due to the effect of the charge diminution at oxygen of the acetate ion by fluorine substitution [22]. Electronwithdrawing groups such as F produce significant changes in the electron density distribution of a molecule or molecular ion.…”

The Structure and Thermodynamics of Ion Association and Solvation of Some Thiocyanates and Nitrates in 2-Methoxyethanol Studied by Conductometry and FTIR Spectroscopy

“…The conductance data have been analyzed by the 1978 Fuoss conductance−concentration equation. , For a given set of conductivity values ( c j ,Λ j ; j = 1, ..., n ), three adjustable parameters, the limiting molar conductivity (Λ 0 ), the association constant ( K A ), and the cosphere diameter ( R ), are derived from the following set of equations: where the symbols have their usual significance. The computations were performed on a computer using the program as suggested by Fuoss. , The initial Λ 0 values for the iteration procedure were obtained from Shedlovsky extrapolation of the data. Input for the program is the set ( c j ,Λ j ; j = 1, ..., n ), n , D , η, T , initial value of Λ 0 , and an instruction to cover a preselected range of R values.…”

“…The non-Coulombic contribution to the Gibbs energy, Δ G *, has been calculated from the following equation: where the symbols have their usual meaning. The quantity 2 q/r is the Coulombic part of the interionic mean force potential, and is its non-Coulombic part.…”

“…The computations were performed on a computer using the program as suggested by Fuoss. 12,18 The initial Λ 0 values for the iteration procedure were obtained from Shedlovsky extrapolation 14 of the data. Input for the program is the set (c j ,Λ j ; j ) 1, ..., n), n, D, η, T, initial value of Λ 0 , and an instruction to cover a preselected range of R values.…”

Thermodynamics of Ion Association and Solvation in 2-Methoxyethanol: Behavior of Tetraphenylarsonium, Picrate, and Tetraphenylborate Ions from Conductivity and Ultrasonic Data

“…The non-Coulombic part of the Gibbs energy, ∆G*, has also been calculated using the following equation 30 :…”