Electrolyte-Solvent Interaction. VIII. Tetrabutylammonium Salts in Nitrobenzene-Carbon Tetrachloride Mixtures at 25°^1,2

Voltammetry of tetraalkylammonium picrates at water∣nitrobenzene and water∣dichloroethane microinterfaces; influence of partition phenomena

“…Contrary to what has reasonably been postulated for nitrobenzene, electrolytes cannot be considered to be fully dissociated in dichloroethane; due to the much lower dielectric constant ((e 25°C = 10.4), association phenomena are important [35]. As an example, the association constant for tetrabutylammonium picrate is 200 times higher in DCE than in NB (log K NB ¼ 1:11 [34]; log K DCE ¼ 3:43 [42]).…”

“…This would require one to know the ion-pair dissociation constants of picrates in wet DCE. Hirsch and Fuoss have shown that precision on the measurements of ion-pair formation constants by conductimetry is low in poorly dissociating media [35]. Calculation of these ionic interactions would be an extensive task, quite imprecise and outside the scope of the present study.…”

“…From measurements by conductimetry, it appears that the dissociation constants of the tetraalkylammonium picrates in nitrobenzene are rather high (10 À1.5 < log K < 10 À1.0 ) [34,35]. The degree of dissociation of the four R 4 N + salts in pure NB, at a concentration of 10 À3 M, is higher than 0.97, so that the picrates have been considered to be fully dissociated in nitrobenzene saturated with water.…”

Conductivity studies of ion pairing in transition metal organics

“…3 represents data collected in CH3CN, D = 35.99,17 and also analyzed according to eq 4 whereas Figure 4 illustrates the same data treated according to the complete Fuoss-Hsia equation, rewritten in the linear form of eq 5. 18 All symbols = 0 -c yf± 2 A/AD (5) in eq 4, 5, and 6, the Debye-Huckel activity coefficient for -ln/± = e2K/2DkT(l + nay112)…”

Effect of the supporting electrolytes on voltammetry at liquid/liquid microinterfaces between water and nitrobenzene, 1,2-dichloroethane or 1,6-dichlorohexane

“…These authors were well aware of the problem of ion-pairing in such solutions and consequently attempted to evaluate ion-pair formation constants by conductimetry, but all the constant reported by these authors are lower than 150 M À1 . These values are much too low for DCH, which permittivity is 8.83; in a NB/CCl 4 mixture having the same dielectric constant, Hirsch and Fuoss measured the constant for ion-pairing of TBAPi to be 10 5 M À1 [34] and, as reported above, the constants for the ion-pair formation are about 10 3 -10 4 M À1 in ethylene chloride (e = 10.2) and 10 4 -10 5 M À1 in dichloromethane (DCM) (e = 8.94). In the absence of accurate values for these association constants, it is impossible to derive the exact ionic concentrations at equilibrium but also, as a consequence, the ionic strength and the activity coefficients of the species, which does not allow the calculation of the exact equilibrium conditions.…”