PKa predictions of some aniline derivatives by ab initio calculations

: In this work, different levels of theory containing HF, B3LYP, and MP2 with different basis sets such as 6-31G, 6-31G*, 6-311G, 6-311+G, 6-31+G*, 6-31+G are used to predict relative acidity constants of some aniline derivatives. Three different kinds of radii containing UAHF, Bondi, and Pauling are used to study how cavity forms change acidity constants. In all cases, DPCM model is used to simulate solvation Gibbs free energy. Furthermore, one similar level and basis set has been linked to IEFPCM and DPCM models to compare the results. To relate gas-phase Gibbs free energy to the solution Gibbs free energy, a simple thermodynamic cycle is used. Results show that quantum chemical calculations are robust techniques for estimating acidity constants.