Abstract
When alkaline aqueous solution of thiamine (I) is allowed to stand in contact with air at 25°, oxidation of the thiol-type thiamine (III) chiefly occurs. Thiamine disulfide (IV), bis (1-acetyl-3-hydroxypropyl) disulfide (X), and 3-mercaptopropanol (XI) formed in this case were followed by polarography and the formation of thiothiazolone compound (VI) was measured by the optical density at 320mμ (cf. Tables I and II). For example, percentage composition of the sample solution after 146 hours was as follows: At pH 9.3: (I) 15, (IV) 65, (VI) 10, (XI) 1.3; at pH 104 (I) 14, (IV) 35, (VI) 11, (XI) 8.3; at pH 12.0: (I) 25, (IV) 13, (VI) 11.5, (XI) 17. When the same solution is allowed to stand in nitrogen atmosphere at 25° or heated to 100°, hydrolysis of the thiazole portion of thiamine chiefly occurs, forming (X), (XI), (VI), and 3-acetyl-3-mercaptopropanol, and this was similarly measured. For example, the percentage composition of the sample solution left in nitrogen atmosphere at 25° for 146 hours was as follows: at pH 9.3: (I) 48, (IX) 13, (VI) 11; at pH 10.4: (I) 20; (IX) 20, (VI) 20; at pH 12: (I) 49, (IX) 4.7, (VI) 15, (XI) 3.6.
