OZONATION OF SULFUR-CONTAINING ALIPHATIC-COMPOUNDS IN AQUEOUS-SOLUTIONS .2. CYSTEINE, CYSTINE AND THIOGLYCOLIC ACID

In view of the possible reaction of ozone with sulfur-containing natur al and anthropogenic compounds, the ozonation of cysteine, cystine, th ioglycolic acid and their oxidation products at pH 3 and 7 (initial co ncentration 1 mmol/L) was investigated. The oxidation of cysteine at p H 3 leads to cysteic acid; at pH 7 sulfoacetic acid, sulfate, ammonia and nitrate are formed besides cysteic acid. Cysteinesulfinic acid as intermediate oxidation product was not identified because of the very fast reaction with ozone forming cysteic acid. The ozonation of cystin e at pH 3 leads to cystinedisulfoxide and finally to cysteic acid. At pH 7, however, disulfoxides as intermediates were not detected. As oxi dation products, cysteic acid, sulfoacetic acid, sulfate, ammonia and nitrate were found. The mass balances show that at pH 7, nitrogen-cont aining organic compounds as intermediates should have been formed, but were not identified. Thioglycolic acid ozonation at pH 7 leads to the formation of dithiodiglycolic acid. After 100% elimination of the ini tial compound, only 10% is found in the S-S-splitting product sulfoace tic acid. The absence of sulfate leads to the conclusion that here oxy gen-containing disulfides are formed as intermediates which are slowly oxidized to sulfoacetic acid.