イオンと溶媒の相互作用に関する研究(V) : アセチルアセトン中の塩化物イオン-溶媒間相互作用に関するノート

The free energies of transfer (ΔG^0_<tr>) of the chloride ion from water to such alcohols (ROH) as methanol (MeOH), ethanol (EtOH), 1-propanol (1-PrOH), 2-propanol (2-PrOH), and 1-butanol (1-BuOH) have been determined potentiometrically at 25℃ by using a silver-silver chloride electrode as an indicator electrode. The reference electrode used was a siver-silver perchlorate (0.01 mol <dm>^<-3> in acetylacetone (Hacac)) electrode and the salt bridge was the 0.1 mol <dm>^<-3> tetraethylammonium picrate solution of Hacac. Acetylacetone was a less basic and less acidic amphiprotic solvent and was used as the solvent for the reference electrode and salt bridge. It was also used as the reference solvent in the complexing of the chloride ion with water and alcohols. The ΔG^0_<tr> (Cl^- : H_2O→ROH) values in kcal mol^<-1> (1 cal=4.184 J) were 3.4 for MeOH, 5.4 for EtOH, 5.9 for 1-PrOH, 7.1 for 2-PrOH, and 7.0 for 1-BuOH. The ΔG^0_<tr> (Cl^- : H_2O→Hacac) value was estimated to be 8.4 kcal mol^<-1> by using the values of ΔG^0_<tr> (Ag^+ : H_2O→Hacac) and the solubility products of silver chloride in water and Hacac. The complex formation through hydrogen bonding of the chloride ion with water and alcohols have also been studied in Hacac by potentiometry. The maximum coordination numbers of the chloride ion were detected to be 6 for water, 5 for MeOH, 4 for EtOH, 3 for 1- and 2-PrOH, and 2 for l-BuOH, respectively. The solvent effect on the solvent transfer and the complexing of the chloride ion was discussed in connection with the solvent acidity.