Electrical conductances for some tetraalkylammonium bromides, lithium tetrafluoroborate and tetrabutylammonium tetrabutylborate in propylene carbonate at 25 °C

Abstract

Conductance measurements are reported for several symmetrical tetraalkylammonium bromides, lithium tetrafluoroborate (LiBF,) and tetrabutylammonium tetrabutylborate (Bu,NBBu,) in propylene carbonate (PC) at 25 "C. The data have been analysed by the 1978 Fuoss conductance equation in terms of the limiting molar conductivity, A', the association constant, K , , and the association distance R. The single-ion conductances have been determined from the A' value of Bu,NBBu, using it as a 'reference electrolyte'. The results indicate that with the exception of LiBF, to some extent, other salts are almost unassociated in this solvent medium. The evaluation of Stokes radii of the ions indicate that Li+ is extensively solvated while the other ions remain almost unsolvated. The results have been discussed in terms of the ion-solvating ability of PC and also compared with the previous values in this system.Propylene carbonate (PC) has drawn much attention in recent years as a solvent medium for electrochemical studies' relating to high-energy batteries2v3 and free-radical species., It is a stable solvent of moderately high relative permittivity5 (64.40 at 25°C) and has good solvent properties6*' for a variety of organic and inorganic salts. Hence, it is of much interest to study the behaviour of electrolytes in such a solvent medium. The conductometric method is well known' to give valuable information regarding ion-solvent interactions of electrolytes in non-aqueous and mixed solvents. Although conductance measurements on alkali-metal iodides9-' and quarternary ammonium perchlorates6*' ' have been reported in PC, no such experimental data for tetraalkylammonium bromides (except tetrabutylammonium bromide) and lithium tetrafluoroborate are available in the literature.Conductance measurements on tetrabutylammonium tetrabutylborate have been reported by Takeda and co-workers,12 but this compound has been further investigated by us in order to maintain an internal consistency amongst the derived values with these electrolytes.We have therefore repeated a few of the earlier measurements and have also measured the electrical conductances of several additional tetraalkylammonium bromides, R,NBr (R = methyl to heptyl), LiBF, and Bu,NBBu, in PC at 25 "C. Single-ion conductances have been derived using Bu,NBBu, as the 'reference electrolyte' in an effort to provide reliable values of the ionic mobilities for these ions in this medium. ExperimentalPC (Merck >99% pure) was dried over freshly ignited quicklime for several hours13 and then distilled three times under reduced pressure under nitrogen, the middle fraction being taken each time. The purified sample had a density of 1.1988 g cm-3, viscosity of 2.471 CP and a specific conductance of ca. 0.73 x S cm-' at 25°C; these values are in good agreement with the literature values.' ', 14 Tetraalkylammonium bromides were of purum or puriss grade (Fluka) and were purified as described in the literature.' 5 * 1 6 The salts were purified by recrystallization and the higher homologues we...

Ionic mobility and ionic association of singly charged ions in glycerol

“…K Ã is the overall pairing constant obtained from the association constants of formation of contact pairs K S and There have been previous analyses of the concentration dependence of the molar conductivity in nonaqueous solutions according to the algorithm developed by Fuoss [1][2][3][4]22]. All of these studies fitted the experimental data with constant values of R and over the whole concentration range 0.5<C < 100 mol m À3 , deducing as a result the value of K Ã .…”

“…His model was further tested by Champeney and Ould Kaddour [3]. This model was also used by Muhuri and Hazra in 1991 [4] and Christie and Vincent in 1996 [5] to determine the conductimetric pairing constants relative to the formation of ion pairs of LiBF 4 and LiPF 6 in propylene carbonate, the main constituents of novel lithium batteries. The Fuoss formalism of ion pairing was adopted by Chou and Tanioka in 1998 [6] to estimate the effective ion concentration in the external solutions of ion-exchange membranes.…”

Global tricompartmental analysis of the fluorescence decay surface of the charged fluorescent probe N,N,N-trimethyl-3-(1-pyrenyl)-1-propanaminium prchlorate

“…According to the identifiability study in section 2.1, the knowledge of kol, k o 2 , and ko3 allows one to specify limits on k21, k31, k12, k32 (eqs [30][31][32][33]. If one of these four rate constants is kept constant at a certain preset value, the system becomes identifiable.…”

Pulsed-Field Gradient NMR Self Diffusion and Ionic Conductivity Measurements for Liquid Electrolytes Containing LiBF4 and Propylene Carbonate

“…Other methods have been employed to probe the ion-ion interactions such as Raman spectroscopy as well as using the Walden product and limiting molar conductivities [16,17], however the use of the Nernst-Einstein equation to predict conductivity was been proven to be effective for both liquid electrolytes [18,19,20,21,22,23] and polymer gel electrolytes [24,25,26,27] and has been shown to yield a good approximation of the ionic interactions.…”