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Physicochemical characterization of sildenafil: Ionization, lipophilicity behavior, and ionic-partition diagram sturdied by two-phase titration and electrochemistry

Gobry, V.
Bouchard, Géraldine
Testa, Bernard
Girault, H. H.
Published in Helvetica Chimica Acta. 2000, vol. 83, no. 7, p. 1465-1474
Abstract 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 12-dichloroethane/H2O system. The dissociation constants (basic pK(a) = 6.78, acidic pK(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
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Deposited on : 2010-08-06

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