Determination of the pKa values of some biologically active and inactive hydroxyquinones
| Autor: | Fabiane C. de Abreu, Cicero de Oliveira Costa, Dorota Zarzeczanska, Tadeusz Ossowski, Piotr Falkowski, Paulo Rogério Barbosa de Miranda, Marília O. F. Goulart, Adam Liwo, Antônio Euzébio Goulart Santana |
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| Jazyk: | angličtina |
| Rok vydání: | 2008 |
| Předmět: |
chemistry.chemical_classification
Ethanol acid dissociation constants hybrid pH-metric/UV titration Stereochemistry Salt (chemistry) Biological activity General Chemistry pH-metric titration Enol Acid dissociation constant Dissociation constant chemistry.chemical_compound molluscicidal activity chemistry hydroxyquinones Computational chemistry Ammonium Titration |
| Zdroj: | Journal of the Brazilian Chemical Society v.19 n.1 2008 Journal of the Brazilian Chemical Society Sociedade Brasileira de Química (SBQ) instacron:SBQ Journal of the Brazilian Chemical Society, Volume: 19, Issue: 1, Pages: 175-183, Published: 2008 |
| Popis: | The apparent dissociation constants (pKa) of four 2-hydroxynaphthoquinones, differently substituted at C-3, were determined in water:ethanol (1:1, v/v) solutions by pH-metric and hybrid pH-metric/UV titration methods. Isolapachol (pKa < 6) was more acidic than lapachol (pKa > 6). Two pKa values were determined for each of the methylamino-derivatives investigated, the first relating to the enol function and the second to the ammonium salt. It was determined that under physiological pH, these derivatives would be to a large extension, zwitterionic. The possible effects of the measured parameters on the biological activities of the studied compounds are discussed. As constantes de dissociação aparentes (pKa) de quatro 2-hidroxinaftoquinonas, diferentemente substituídas em C-3, foram determinadas em meio aquoso-etanólico (1:1, v/v), utilizando titulações pH-métricas e espectrofotométricas. O isolapachol (pKa6). Os derivados 3-metilaminados apresentam dois valores de pKa, um relacionado ao grupo enólico e o outro ao sal de amônio, e são zwitteriônicos, em larga extensão, em pH fisiológico. As possíveis conseqüências desses parâmetros frente a suas atividades biológicas são discutidas. |
| Databáze: | OpenAIRE |
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