Oxyhalogen–sulfur chemistry: non-linear oxidation of 2-aminoethanethiolsulfuric acid (AETSA) by bromate in acidic medium
Abstract
The reaction between bromate and 2-aminoethanethiolsulfuric acid, H2NCH2CH2S—SO3H (AETSA), has been studied in high acid environments. The stoichiometry in excess AETSA is BrO3–+ H2NCH2CH2S—SO3H + H2O → H2NCH2CH2SO3H + SO42–+ 2H++ Br–. In excess BrO3– the stoichiometry is: 7BrO3–+ 5H2NCH2CH2S—SO3H → 5Br(H)NCH2CH2SO3H + 5SO42–+ Br2+ 3H++ H2O. The reaction displays clock reaction characteristics in which there is initial quiescence followed by a sudden and rapid formation of Br2(aq). The oxidation proceeds by successive addition of oxygen on the inner sulfur atom followed by cleavage of the S—S bond to form taurine and SO42–. The Br2(aq) and the HOBr in solution oxidize the taurine to form a mixture of monobromotaurine and dibromotaurine. Computer simulations of a proposed 13-step reaction scheme produced a reasonable fit to the experimental data.
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