Solvent Effect on Protonation Constants of L-alanine and Alanine Methyl ester in Different Aqueous Solutions of 1,4-Dioxane

The protonation constants of alanine and alanine methyl ester were determined in different aqueous solutions of 1,4-dioxane containing (0-50% v/v), using a potentiometric method at 25oc and constant ionic strength 0.1 mol.l-1 (nacl). the protonation constants were analyzed in terms of kamlet, abboud and taft (kat) parameters. the results show that the effect of β is higher in comparison with the other parameters (α and π*). single-parameter correlation of the constants versus α, β, and π* are poor in all solutions. but multi-parameter correlation represents significant improvements with regard to the single- parameter models .