Abstract
Physicochemical properties of thiaminic acid (TnA) and its O-benzoyl ester (BTnA) were investigated. The ultraviolet absorption maxima were shifted with the change of pH and the isobestic point was at 273 mμ. BTnA is sparingly soluble in water showing an increase of the solubility at above pH 6.0,while TnA is soluble at various pH. They are negative to Dragendorff's reagent, or on thiochrome reaction even after treating with cysteine or thiosulfate. However, they are colored to blue by the tert-butyl hypochlorite method. Rf value of TnA is 0.25 and that of BTnA is 0.54,when developing solvent consisted of n-butanol, acetic acid and water is used. They were proved to have properties of amphoteric electrolyte by paper electrophoresis. Appearent pK_1 (SO_3H) and pK_2 (NH_3^+) obtained by the titration curves were 2.2 and 6.2,and isoelectric points were caluculated as pH 4.2. By the hydrolysis of TnA with hydrochloric acid, 2-methyl-4-amino-5-aminomethylpyrimidine and formic acid were produced, and in the case of BTnA, benzoic acid was also obtained.
