![]() ![]() ![]() Various physico-chemical techniques such as: spectrophotometry, NMR spectrometry, polarography, potentiometry and conductometry have been used to study the complex formation between macrocyclic polyethers (crown ethers) and various metal cations in solutions. Iodine has been found to form with many compounds charge transfer complexes whose properties have been thoroughly studied. During the past two decades, a growing interest has been focused on the complexing ability of these macrocyclic ligands as electron-pair molecules towards neutral and, especially, molecular iodine. The stability of these complexes appears to be related to the macrocycles, cavity sizes It is at maximum when the cavity diameter matches the ionic size. Crown ethers are macrocyclic ethers known for their ability to form stable and selective inclusion complexes with many metal ions, including alkali and alkaline earth metal cations. Studies of crown ethers complexation in different solvents show that the thermodynamic and kinetic parameters and even the mechanism of the complexation processes are affected by the nature and composition of the solvent system. Many investigations have been carried out on applications of crown ethers in several varieties of areas, such as: chemical analysis, in construction of ion-selective electrodes, solid phase in chromatography column. Lariat ethers belong to special class of crown ethers with covalency linked side arm(s), which enhance the binding ability of crown ethers towards metal ions. Keywords: Iodine Charge transfer complex Spectrophotometry Kinetic Crown ether. ![]() The pseudo first order rate constants were evaluated from the absorbance- time data and found to vary in the order of 1,2-DCE >DCM >CHCl 3. The rate of formation of product has been measured as a function of time in different halocarbone solvents. The pseudo-first-order rate constants for the formation of the ionic intermediate and the final product have been evaluated at 25 ☌. The results indicated immediate formation of an electron donor-electron acceptor complex which is followed by two relatively slow consecutive reactions. e-mail: complexation of iodine with 15-crown-5(15C5), dicyclohexyl-18-crown-6 (DC18C6), benzo-18-crown-6 (B18C6) and dibenzo-24-crown-8 (DB24C8) has been studied in chloroform (CHCl 3), Dichloromethane (DCM) and 1,2-dichloroethane (1,2-DCE) solutions at different time. *Department of Chemistry, University of Guilan, P.B. KINETIC STUDY OF CHARGE TRANSFER COMPLEXES OF IODINE WITH SOME CROWN ETHERS IN NONAQUEOUS SOLVENTS ![]()
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