Sodium diethyldithiocarbamate

The conductance of sodium diethyldithiocarbamate (NaDDC) has been measured in acetonitrile-water mixtures at 25°C where the dielectric constant (D) ranges from 46.52 up to 74.66. Using Fuoss-Onsager theory, the data was interpreted to obtain Λ o , K A and å values. For NaDDC, the ion parameter å (express the solvation) and limiting equivalent conductance Λ o decrease with decreasing the dielectric constant of the medium until it reaches a minimum and then increases again. The increase in log K A versus 1/D plot shows the dominance of electrostatic interaction. By applying the solvent separated – ion pair model, the association constant (K A) is analyzed.

The conductance data of sodium diethyldithiocarbamate (NaDDC) in water solutions at various temperatures (25, 30, 35 and 40°C) are presented. The results were construed by applying the Fuoss-Onsager equation to obtain the parameters: equivalent conductance at infinite dilution (Λ o), the distance of closest approach (å) and association constant (K A). In the light of the solvent separated-ion pair model, the K A trend is discussed. A comparison was done between the value of å and the sum of calculated electrostatic Stokes' radii R + and R-. Both of thermodynamic functions (ΔH o , ΔG o , ΔS o) and the activation energy (ΔE s) were determined; the Λ o values were noticed to increase gradually with the dramatic increase in temperature referring to less solvation or higher ions mobility. Negative values of Gibbs free energy change ΔG o for (NaDDC) indicate that the association process is preferable than the dissociation process. The positive value of (ΔH o) points to that the association process is endothermic. Entropy change (ΔS o) values were positive which means that the solvation of ion-pair decreases emulated to that of the free ion.