Theory And Experiment Study On Interhalogen Compounds

Interhalogen compounds play an important role in the organic synthesis and chemistry analysis field. This dissertation mainly includes theory research and experiment research for the interhalogen compounds(BrCl,IBr and ICl).For the theory research part, the density functional theory (DFT) in the quantum chemistry has been employed to investigate the gas reaction mechanism particularly for Br₂+Cl₂=2BrCl, Br₂+I2=2IBr and I2+Cl₂=2ICl. The 3-21G** basis set has been employed for iodine-containing reactions and the 6-311G** basis set for other reactions. The following results and conclusions have been reached: (1) Reactions Br₂+Cl₂=2BrCl, Br₂+I2=2IBr and I2+Cl₂=2ICl occur more easily in the bimolecular form without energy. (2) The bimolecular elementary reactions have different four-center transition states. Among these four-center transition states, the transition state with"Z"form is the most stable. All the four-center transition states are planar. (3) The active energy for the reactions Cl₂+Br→BrCl+Cl and I+Cl₂→ICl+Cl is 19.09 and 6.12KJ/Mol; and for the reactions Cl₂+Br→BrCl+Cl, I+Br₂→IBr+Br, I2+Br→IBr+I, I2+Cl→ICl+I take place first via processes without energy barrier to form stable molecules BrCl₂, IBr₂, I2Br and I2Cl, then the energy of systems increase steadily and the molecules decompose to products.For the experiment research part, the chlorine, bromine and iodine were prepared carbon tetrachloride solution in the same concentration, and then the same volume solution were mixed respectively, these mixed solutions were put under the ultraviolet radiation and in the dark respectively. The absorbency of the mixed solutions was determined with UV spectrophotometer every determinate time. The experiment results show: the reaction rate for the gas reactions Br₂+Cl₂=2BrCl, Br₂+I2=2IBr and I2+Cl₂=2ICl in the dark is slower than that with ultraviolet radiation; which indicated that Cl₂,Br₂ and I2 are split into free radicals firstly, and then this free radical reacts with another molecule through a three-center transition state to form the product, so the reaction rate is rapid when the ultraviolet radiation exists.So, the same conclusions can be achieved by the theory research and experiment...