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Physicochemical Characterization of Sildenafil: Ionization, Lipophilicity Behavior, and Ionic‐Partition Diagram Studied by Two‐Phase Titration and Electrochemistry
Author(s) -
Gobry Véronique,
Bouchard Géraldine,
Carrupt PierreAlain,
Testa Bernard,
Girault Hubert H.
Publication year - 2000
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20000705)83:7<1465::aid-hlca1465>3.0.co;2-#
Subject(s) - chemistry , lipophilicity , electrochemistry , phase diagram , ionic bonding , ionization , titration , characterization (materials science) , phase (matter) , inorganic chemistry , partition coefficient , analytical chemistry (journal) , computational chemistry , ion , chromatography , organic chemistry , nanotechnology , electrode , materials science
Sildenafil ( Viagra TM ) was examined for its ionization and lipophilicity by two‐phase titration and electrochemistry at the interface between two immiscible electrolyte solutions (ITIES) in the 1,2‐dichloroethane/H 2 O system. The dissociation constants (basic p K a =6.78, acidic p K a =9.12) and partition coefficients of the various species, together with the effects of electrical potential, were used to construct an ionic partition diagram (pH‐potential representation). This allowed to interpret the transfer mechanisms of sildenafil at liquid/liquid interfaces, suggesting in particular that an intramolecular H‐bond influences the lipophilicity of the neutral and cationic species. Conformational calculations confirmed this hypothesis.