1992 Volume 65 Issue 4 Pages 1012-1015
The acid dissociation constants of the hydroxyl groups in tetrasodium 25,26,27,28-tetrahydroxycalixarene-5,11,17,23-tetrasulfonate (CALX-S4) were determined at 25 °C by potentiometric and spectrophotometric titration methods. The first acid dissociation constant(pKa1) was found to be 3.26 ± 0.02 (μ = 0.1 with KNO3), which demonstrated a remarkable pKa shift due to intramolecular hydrogen-bonding interactions among the hydroxyl groups in CALX-S4. On the other hand, considerably weak acidities were observed on the residual three hydroxyl groups of CALX-S4 (pKa2 = 11.8 ± 0.3 (μ = 0.1 with KNO3), 11.3 ± 0.3 (μ = 2.0 with KCl), pKa3 = 12.8 ± 0.3 (μ = 2.0 with KCl), and pKa4= ca. 14 (μ = 2.0 with KCl)).
This article cannot obtain the latest cited-by information.