Conductometric and spectroscopic studies of the ion-pair association of sodium and potassium picrate in 2-butanone

摘要

The specific conductance of different concentrations of both sodium picrate and potassium picrate in 2-butanone have been measured experimentally at 298 K. The conductance data were analyzed by applying the Lee-Wheaton conductance equation where the molar conductance, the limiting molar conductance and the ion-pair association constant K_A (cond) were calculated, and discussed. Also the spectra of solutions of both sodium picrate and potassium picrate in 2-butanone at 298 K in the range of 330-450 nm have been measured as a function of salt concentration and in the presence of added sodium tetraphenylborate. The spectrum of tetran-butylammonium picrate has also been measured. The spectra are consistent with two species being present in sodium picrate and potassium picrate solutions, the free ions and ion pairs. From the spectroscopic measurements, the ion-pair association constant of both sodium picrate and potassium picrate have been calculated and discussed. Values of the ion-pair association constant obtained from spectroscopic study are significantly larger than the value obtained from conductance measurements. The possible significance of the observations that K_A (spec) > K _A (cond) for the systems under investigation in 2-butanone is discussed.