Journal
JOURNAL OF SEPARATION SCIENCE
Volume 31, Issue 14, Pages 2686-2693Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/jssc.200800227
Keywords
acidity constant; azahelicenes; capillary electrophoresis; ionization constant; non-aqueous capillary electrophoresis
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Funding
- Grant Agency of the Czech Republic [203/06/1044, 203/08/1428, 203/07/1664]
- European Commission [FP6-015847]
- Ministry of Education (Center for Biomolecules and Complex Molecular Systems [LC512]
- Research Project [0021620857, Z40550506]
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CZE was employed to determine acid-base dissociation constants (pK(a)) of ionogenic groups of azahelicenes in methanol (MeOH). Azahelicenes are unique 3-D aromatic systems, which consist of ortho-fused benzene/pyridine units and exhibit helical chirality. The pK(a) values of pyridinium groups of the studied azahelicenes were determined from the dependence of their effective electrophoretic mobility on pH by a nonlinear regression analysis. The effective mobilities of azahelicenes were determined by CZE at pH range between 2.1 and 10.5. Thermodynamic pK(a) values of monobasic 1-aza[6]helicene and 2-aza[6]helicene in MeOH were determined to be 4.94 +/- 0.05 and 5.68 +/- 0.05, respectively, and pK(a) values of dibasic 1, 14-diaza[5]helicene were found to be equal to 7.56 +/- 0.38 and 8.85 +/- 0.26. From these values, the aqueous pK(a) of these compounds was estimated.
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