Acid-base equilibria of the sodium salt of 3,5,7-trihydroxy-2-(3,4-dihydroxy-5-sulfophenyl)-4(4H)-chromenone and its complexes with magnesium and calcium ions

Authors
Bujonek, B Kopacz, M Nowak, D
Citation
B. Bujonek et al., Acid-base equilibria of the sodium salt of 3,5,7-trihydroxy-2-(3,4-dihydroxy-5-sulfophenyl)-4(4H)-chromenone and its complexes with magnesium and calcium ions, RUSS J G CH, 69(12), 1999, pp. 1942-1945
Citations number
6
Categorie Soggetti
Chemistry
Journal title
RUSSIAN JOURNAL OF GENERAL CHEMISTRY
ISSN journal
10703632 → ACNP
Volume
69
Issue
12
Year of publication
1999
Pages
1942 - 1945
Database
ISI
SICI code
1070-3632(199912)69:12<1942:AEOTSS>2.0.ZU;2-U
Abstract
Acid-base equilibria of the sodium salt of 3,5,7-trihydroxy-2-(3,4-dihydrox y-5-sulfophenyl)-4(4H)-chromenone were studied by potentiometric titration. The four dissociation constants were determined: pK(a1) 7.43 +/- 0.03, pK( a2) 8.16 +/- 0.04, pK(a3) 9.24 +/- 0.02, and pK(a4) 10.84 +/- 0.04. The com plexation equilibria of the sodium salt with Mg2+ ions in aqueous solutions were studied, and the stability constant beta(1) of the ML complex was det ermined to be 7.95 x 10(2). Solid magnesium and calcium complexes M(C15H9O1 0S)(2). 8H(2)O (M = Mg, Ca) were isolated.