Nucleophilic aromatic substitution of phenoxy from 2,4-dinitrodiphenylether with dimethylamin was carried out in the gas-phase using theoretical methods; semi-empirical PM6, density functional theory B3LYP/6-31G* and hatreefock HF/3-21G. Calculations were done for the reactants and transition states in which the properties of the system are known and parameters such as the Entropy, Enthalpy and Gibb’s free energy were calculated for both the reactant and the product and their change evaluated. The reaction follows a second order kinetics and all methods gave a good fit for Arrhenius Equation indicating that as the temperature rises, the specific rate constant increases accordingly. All the methods gave negative values of ΔS, density functional gave the most negative value for change in entropy, semi-empirical PM6 has the highest value for activation energy but the lowest value of rate constant arising from the high value of Gibb’s free energy, Hatreefock gave the highest values for both pre-exponential factor and the rate constants. The rate of reaction is temperature dependent but not feasible at temperatures below room temperature.
Keywords : Nucleophilic substitution; rate constants; temperature