Determination of the pKa values of some biologically active and inactive hydroxyquinones

Journal of the Brazilian Chemical Society

Sant’Ana, Antônio Euzébio G.¹  Ossowski, Tadeusz¹  Goulart, Marília O. F.¹  University of Gdansk, Poland¹  Falkowski, Piotr¹  Abreu, Fabiane C. de¹  Liwo, Adam¹  Universidade Federal de Alagoas, Maceió, Brazil¹  Zarzeczanska, Dorota¹  Costa, Cicero de Oliveira¹  Miranda, Paulo Rogério B.¹ 

关键词: acid dissociation constants;    hydroxyquinones;    pH-metric titration;    hybrid pH-metric/UV titration;    molluscicidal activity;   

DOI  :  10.1590/S0103-50532008000100025

学科分类：化学（综合）

来源: SciELO

【 摘 要 】

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.

【 授权许可】

Unknown