A computational study on the rate constant of the SN2 reactions in the gas and solvent phases

SN2 reactions are characterized by an exchange of substituents between two species and have the general form: These reactions proceed via a collision between the reactants, with the nucleophilic species attacking the opposite side of the molecule with respect to the ionic substituent that it liberated. such a process yield a transition structure in which the ion and neutral reactant are weakly bound. All of the calculations were done in the gas and solvent(water); indeed, the properties of molecules and transition states can differ considerably between the gas phase and solution. In this process, kinetics parameters of reactions between Chlorocyclopropane, Chlorocyclobutane, Chlorocyclopentane and Fluoride ion in the gas and solvent phases are calculated. All geometries [reactants, products, complexes and transition state(TS)] were full optimized at the Hartree-Fock level of theory using the standard 6-311+G(d,p) basis set under the Gaussian03 program. Transition state structures obtained from QST3 with converting reactants to products. Additionally, rate constants have been obtained utilizing Transition State Theory (TST).