Coulometric generation of protons by oxidation of hydrogen dissolved in palladium, in non-aqueous media.
Coulometric generation of H(+) ions by the oxidation of hydrogen dissolved in palladium, in media such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, acetic anhydride and acetic acid-acetic anhydride mixture, for use in titration of bases, has been investigated. The hydrogen is oxidized at potentials which are much more negative than those of the bases and other components present in the solution. Titrations of numerous bases have established that the oxidation is quantitative and proceeds with 100% current efficiency.
Potentiometric determination of pK(A) of organic bases in acetone by the application of coulometry.
A coulometric-potentiometric method for the determination of pK(A) values of organic bases in anhydrous acetone is described. The bases were titrated with protons obtained by anodic oxidation of hydrogen dissolved in palladium, in the presence of sodium perchlorate as the supporting electrolyte. A pair of glass electrodes was used for measuring directly the difference between the half-neutralization potentials of the standard and the base being studied. The pK(A) values obtained were close to those reported in the literature. The effect of the supporting electrolyte concentration on the pK(A) values of some of the bases was also studied.
Chemical constituents and chemotaxonomic study of Glycyrrhiza pallidiflora maxim
Abstract Phytochemical study of Glycyrrhiza pallidiflora Maxim. gave seventeen compounds, including two sterols (3 and 4), four triterpenes (1, 2, 5, 6), ten flavones (7, 9–17), and one pterocarpan (8). The chemotaxonomic significance of G. pallidiflora was discussed, which indicated the close relationship between G. pallidiflora with other species of Glycyrrhiza. Moreover, pallidiflorin can be served as a fingerprint for G. pallidiflora, macedonic acid and echinatin can be recognized as biomarkers for Glycyrrhiza, while formononetin, afrormosin and calycosin may be typical second metabolites for Papilionoideae.