Chemical Oxidation of Phthalmic Drug Timolol by Peroxodisulfate

The oxidation of morpholine-thiadiazol based structure ophthalmic beta blocker drug, Timolol, in the presence of Potassium Perxodisulfate (PDS) and 40% methanol-water has been studied using spectrophotometric method. It has been found that; oxidation reaction starts with electrophilic attack of PDS species on the protonated form of Timolol leading to produce three products (I,II and III) one of them retains the morpholne-thiadiazole structure (I). The products were characterized as (I) 4-morpholino-1,2,5-thiadiazol-3-ol, (II) 3-(carboxy diformylmethylamino)-2-hydroxypropanoic acid and (III) 2-(2-formyl-2-hydroxyethylamino)-2,2-diformylacetic acid. The detailed mechanism of the oxidation reaction was proposed, and thermodynamic parameters were obtained for different reaction steps.