Abstract
A mechanistic study has been performed on the complex reaction between thiocyanate and iodate in acidic medium. A 14-step mechanism is proposed in which the first step of the oxidation is I03" + SCN' + 2H+ -*· HOSCN + HI02. The HOSCN is then oxidized rapidly by either HI02 or I2 to give S042
The transient formation of I2 in excess thiocyanate is attributed to a competition between the Dushman reaction, I03" + 51' + 6H+ -* 3I2 + 3H20, which is strongly catalyzed by acid, and slower, acid-inhibited reactions, which consume iodine. The consumption of iodine by thiocyanate proceeds via the rapid formation of the I2SCN" complex, which later hydrolyzes to give HOSCN. Other observed reaction dynamics have been explained through the same proposed mechanism. Computer simulation using this mechanism gives good agreement with experiment.