2010 Volume 9 Issue 4 Pages 205-210
Using molecular mechanics with amber potential, we investigated the reaction mechanism of an iodine precipitation reaction induced solute freezing process or the in macro ice solid phase of iodide ionic acidic solution. Though a redox reaction such as iodine precipitation in iodide ionic acidic solution is usually difficult to proceed even in high temperature, the reaction: I- →I • +e- and I • +I • →I2 were processed in solute freezing process or in macro ice solid phase. As initial geometries, we took structures of I2(H2O)30 cluster where waters are surrounding two iodine atoms. Iodine atoms were located outside of water clusters in all geometries obtained by geometry optimization with Amber potential. Unfortunately, geometry optimizations by PM3 and HF/Lanl2DZ were incomplete because iodine atoms were located outside and dissociated from the water cluster. In low temperature, the contribution of enthalpy for system stabilization is bigger than that of entropy. Water crystallization is enhanced by maximization of the number of hydrogen bonding in the solution. Therefore, precipitation of I2 is realized.
