Protolytic and tautomeric equilibria of pyridoxine in aqueous ethanol

Influence of aqueous dimethyl sulfoxide on pyridoxine protonation and tautomerization

“…The equilibrium pyridoxine concentration in hexane phase was calculated by subtraction of the equilibrium pyridoxine concentration in bottom layer from the total concentration of PN. The partition coefficients of pyridoxine and Gibbs energy change of PN transfer from water to aqueous dimethyl sulfoxide were calculated employing following equations [12]: The results of experiment determining the macroscopic Gibbs energy changes of pyridoxine (without separation on molecular and zwitterionic species yet) from water to aqueous DMSO are given ( Table 2). When DMSO content is N0.5 m.f., binary solvent starts to dissolve noticeably into hexane as it was found by refractometry.…”

“…In the aqueous ethanol, the solvation contributions of charged reagents were predominant at low content of alcohol (contribution of PNH + at X EtOH = 0.1 and H + at X EtOH = 0.2) [12]. In the range of 0.3-0.5 m.f.…”

“…Like in previous study [12], the indicator glass electrode and silver chloride reference electrode were employed: where S is for organic component of binary solvent (DMSO). The potential difference between electrodes was measured with error ± 0.1 mV.…”

“…The study of PN protonation and tautomerization in mixtures of water with other important organic solvent, ethanol, had been carried out recently [12].…”

Solvent effect on protonation of tpps in water-DMF mixtures

“…Spectroscopic titration is a convenient way for accurate determination of equilibrium constants [18][19][20]. In this method, the spectral absorbances during titration are used to construct a matrix R of size mn where m is the number of pH values in which absorbance are determined in n wavelengths.…”