Equilibrium Study on Ion-Pair Formation in Water and Distribution Between Water and m-Xylene of Tetraalkylammonium Picrates |
| |
Authors: | Shoichi Katsuta Takuya Ishitani Mika Suzuki Yuki Ishii Yoshihiro Kudo Yasuyuki Takeda |
| |
Institution: | (1) Department of Chemistry, Faculty of Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba, 263-8522, Japan |
| |
Abstract: | The 1:1 ion-pair formation constants (K
IP) of tetraalkylammonium (Me4N+, Et4N+, Pr4N+, Bu4N+, and Bu3MeN+) picrates in water were determined by capillary electrophoresis at 25°C. The ion-pair extraction constants (K
ex,ip) of the picrates from water to m-xylene were determined by a batch-extraction method at 25°C, and the distribution constants (K
D) of the neutral ion-pairs were calculated from the relationship K
D = Kex,ip/K
IP. The tetraalkylammonium ion having more methylene groups generally forms a slightly more stable ion-pair with the picrate ion in water, which is attributed to the lower hydration of the cation. For Me4N+, Et4N+, Pr4N+, and Bu4N+, the distribution of the ion pair into m-xylene increases in that order, and a linear relationship was found between log K
D and the number of methylene groups in the cation. This is consistently explained by the regular solution theory. It was also revealed that the ion pairs have a strong specific interaction with water. The ion pair of Bu3MeN+ has a higher distribution constant than that expected from the relationship between log K
D and the number of methylene groups for the symmetrical tetraalkylammonium ions. The cation dependence of the ion pair extractability is mostly governed by that of the distribution of the ion pair. |
| |
Keywords: | Ion-pair formation in water liquid– liquid distribution ion-pair extraction tetraalkylammonium picrates capillary electrophoresis regular solution theory |
本文献已被 SpringerLink 等数据库收录! |
|