Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Re-evaluation of the Acid Dissociation Constants of the Hydroxyl Groups in Tetrasodium 25,26,27,28-Tetrahydroxycalix[4]arene-5,11,17,23-tetrasulfonate
Isao YoshidaNobuhiro YamamotoFumio SagaraDaido IshiiKeihei UenoSeiji Shinkai
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1992 Volume 65 Issue 4 Pages 1012-1015

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Abstract

The acid dissociation constants of the hydroxyl groups in tetrasodium 25,26,27,28-tetrahydroxycalix[4]arene-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)).

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© 1992 The Chemical Society of Japan
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