Kinetics and mechanism of the reaction between thiourea and iodate in unbuffered medium  

作　　者：WANG Shun1,2, LIN Juanjuan1, CHEN Fan1, HU Maolin1, HU Xingen1, HAN Yiping1 & GAO Qingyu2 1.Department of Chemistry and Material Science, Wenzhou Normal College, Wenzhou 325027, China 2. College of Chemical Engineering, China University of Mining and Technology, Xuzhou 221008, China 

出　　处：《Science China Chemistry》2004年第6期480-487,共8页中国科学（化学英文版）

基　　金：This work was supported by the National Natural Science Foundation of China(Grant Nos.20103010 and 20073039).

摘　　要：The reaction between iodate and thiourea has been studied in an unbuffered acidic medium. In excess iodate the reaction shows not only oligooscillations in pH, Pt potential and the concentration of iodide ion, [I?], but also an initial induction period which has the linear relation with initial pH. At the end of the induction period, [I?] decreases sharply and a yellow coloration (due to iodine) appears transiently. While in excess thiourea iodine is produced and finally con- sumed, leaving milky deposits (due to sulfur) at the end of the reaction. The induction period from the start of the reaction to the maximum of [I2] is also directly proportional to initial pH. A 14-step mechanism, including a H+-mediated preequalibrium, Dusman reaction, iodine-sulfur reactions and sulfur-sulfur reactions, is proposed. Computer simulations using this mechanism give good agreement with experiments.The reaction between iodate and thiourea has been studied in an unbuffered acidic medium. In excess iodate the reaction shows not only oligooscillations in pH, Pt potential and the concentration of iodide ion, [I], but also an initial induction period which has the linear relation with initial pH. At the end of the induction period, [I] decreases sharply and a yellow coloration (due to iodine) appears transiently. While in excess thiourea iodine is produced and finally consumed, leaving milky deposits (due to sulfur) at the end of the reaction. The induction period from the start of the reaction to the maximum of [I2] is also directly proportional to initial pH. A 14-step mechanism, including a H+-mediated preequalibrium, Dusman reaction, iodine-sulfur reactions and sulfur-sulfur reactions, is proposed. Computer simulations using this mechanism give good agreement with experiments.

关 键 词：oligooscillations  pH dynamics  thiourea  iodate  COMPLEX REACTION mechanism  dynamic simulation. 

分 类 号：O643.1[理学—物理化学]