Abstract
The purification method of acetylacetone (H-AA) has been developed for use as a solvent in electro chemical studies. The commercial H-AA, which contains water, acetone and acetic acid in the range of (0.030.05)v/v%as determined by gas chromatography, was purified by shaking with calcium hydride, followed by distillation under reduced pressure (at ca. 25mmHg and ca. 50°C) in the nitrogen gas atmosphere. The electrolytic conductivity, dielectric constant and viscosity of the purified H-AA were 1×10-8S cm-1, 27.20 and 0.694cP at 25°C, respectively. The water content of the purified H-AA was. ca. 0.01v/v %, but acetone and acetic acid were not detected. Perchlorates of lithium, sodium, and tetrabutyl ammonium (TBAP), and bromide of tetrabutyl ammonium are soluble in H-AA to the extent of more than 1M. The useful potential range in 0.1M TBAP-H-AA is (-0.2-2.25)V at the dropping mercury electrode, and (+0.9-2.35)V at the stationary Pt microelectrode, vs. Ag/0.1M AgClO4 (H-AA). From the conductivity measurements, it is found that alkali metal ions are not strongly solvated in H-AA as in the case of acetone and 2, 2, 2 trifluoroethanol (TFE), and that their salts form contact ion-pairs. On the other hand, small anions such as Cl- and Br- are solvated to a great extent due to the effect of the enol form of H-AA, and, thus, the ion-pairs of tetrabutylammonium halides in H-AA are found to be solvent-separated like those in TFE. Thus, the solvation of H-AA towards cations and anions is very similar to that of TFE which is nearly isodielectric to H-AA and known to solvate anions very effectively through hydrogen bonding.
