Solvent Effect on Protonation Constants of Erythromycin in Different Aqueous Solutions of Methanol and Ethanol
Solvent Effect on Protonation Constants of Erythromycin in Different Aqueous Solutions of Methanol and Ethanol
The protonation constants of erythromycin were measured in binary mixtures of water+metanol and water+etanol containing 0, 10, 20, 30, 40 and 50% (v/v). These measurments were done using the potentiometric method at T = 25 °C and constant ionic strength (0.1 mol.dm-3 of sodium perchlorate). The protonation constants were analyzed using Kamlet-Abboud-Taft (KAT) and normalized polarity parameters (ETN). Dual-parameter correlation of pKa versus π* (dipolarity/polarizability) and α (hydrogen-bond donor acidity) as well as pKa versus π* and β (hydrogen-bond acceptor basicity) gave a good results in mixed solvents of water+methanol and water+ethanol. There is a linear relationship between acidic dissociation constants and mole fraction of alcohol in solvent mixture water+methanol. In this research work, we discussed the solvent effect and dielectric of the area on the acidic dissociation constants of erythromycin.