%0 Journal Article
%T Determination of the pKa values of some biologically active and inactive hydroxyquinones
%A Ossowski
%A Tadeusz
%A Goulart
%A Mar¨ªlia O. F.
%A Abreu
%A Fabiane C. de
%A Sant£¿Ana
%A Ant£¿nio Euz¨¦bio G.
%A Miranda
%A Paulo Rog¨¦rio B.
%A Costa
%A Cicero de Oliveira
%A Liwo
%A Adam
%A Falkowski
%A Piotr
%A Zarzeczanska
%A Dorota
%J Journal of the Brazilian Chemical Society
%D 2008
%I Sociedade Brasileira de Qu¨ªmica, SBQ
%R 10.1590/S0103-50532008000100025
%X 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.
%K acid dissociation constants
%K hydroxyquinones
%K ph-metric titration
%K hybrid ph-metric/uv titration
%K molluscicidal activity.
%U http://www.scielo.br/scielo.php?script=sci_abstract&pid=S0103-50532008000100025&lng=en&nrm=iso&tlng=en