Conductimetric Studies of Ionic Association of Tetraalkylammonium Halides and Tetraphenylborate in N,N-Dimethylformamide–Methyl Ethyl Ketone Mixtures at 25 °C

Abstract

The molar conductivities of Et4NBr, n-Pr4NBr, n-Bu4NBr, and n-Bu4NBPh4 have been measured in N,N-dimethylformamide–methyl ethyl ketone (DMF–MEK) mixtures (34.5≥D≥20.10) over the maximum concentration range (2×D3×10−7 mol dm−3) along with the densities and viscosities of the solvent mixtures at 25 °C. The conductance data have been analyzed by using the Fuoss-1978 (F78) conductance equation and the results compared with those obtained from the Justice (J) and the Fuoss-Onsager-Skinner (FOS) equations. The molar conductivities at infinite dilution (Λ0), the thermodynamic association constant (KA) and the distance or the ion-size parameter (R or a°) are evaluated from these data. A better fit of the parameters was provided by the F78 equation which yielded KA and R values. The Λ0 and the KA values are found to increase with decrease in the dielectric constant of the medium and in a given solvent mixture they follow the order Et4NBr>n-Pr4NBr>n-Bu4NBr>n-Bu4NBPh4.

Ionic Association and Conductances of Some Symmetrical Tetraalkylammonium Salts in Methanol, Acetonitrile, and Methanol (1) + Acetonitrile (2) Mixtures at 298.15 K

“…The values of R are, thus, always higher than a + d, which has a maximum value of 12.05 Å for Hep 4 NBr in acetonitrile, indicating that R 4 N + Brion pairs are solvent separated in all the solvent media investigated. Such large values of R for tetraalkylammonium salts have also been observed in different pure and mixed solvents (Islam et al, 1989;Hazra, 1991, 1995;Srivastava and Samant, 1994).…”

“…(1) dipole interaction (Kay et al, 1965;Islam et al, 1989). For each salt, however, ionic association increases slowly with increasing methanol content in the solvent mixtures.…”

“…Extensive studies on the electrical conductivities in various mixed organic solvents have been performed in recent years (Muhuri and Hazra, 1995;Srivastava and Samant, 1994;Doe et al, 1990;Taniewska-Osinska et al, 1989;Islam et al, 1989;Papadopopulos, 1989;Niazi, 1988) to examine the nature and magnitude of ion-ion and ionsolvent interactions. Such solvent properties as the viscosity and the relative permittivity have also been taken into consideration, which help determine the extent of ion association and the solute-solvent interactions.…”

Ionic Association and Conductances of Some Symmetrical Tetraalkylammonium Perchlorates in 2-Methoxyethanol + Water at 298.15 K

“…The Λ°values of tetraalkylammonium perchlorates decrease as the alkyl chain length increases (Table 3). This is in agreement with earlier findings in several pure and mixed solvents (Fernandez-Prini, 1973;Muhuri and Hazra, 1991;Das and Hazra, 1992;Islam et al, 1989). The size and structure-forming effect decrease as the alkyl chain length increases, and consequently, the mobility is in the reverse order.…”

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“…Aqueous binary mixtures of organic solvent with its varying range of composition are most frequently investigated solvent media [5][6][7][8][9][10][11] .…”