Calculation of acidity/basicity values of some fluorinated compounds in gas phase and aqueous solution: A computational approach

Abstract

In this work, acidity/basicity values calculations of some fluorine compounds in gas and aqueous phases were theoretically performed. The gas phase acidity/basicity values were calculated using various computational series including M05-2X, M06-2X and PBE1PBE functionals combined with 6-31+G(d) and 6-31++G(d,p) and 6-311+G(d,p) basis sets. In addition, single point energy calculations in gas phase were carried out at MP2/6-311++G(3df,3pd), M05-2X/aug-cc-pVTZ and M06-2X/aug-cc-pVTZ levels of theory. Beside, CBS-QB3 method was applied to compare with the obtained acidity/basicity values. Results showed that PBE1PBE functional was better than M05-2X and M06-2X functionals. Also, PBE1PBE/aug-cc-PVTZ//PBE1PBE/6-31+G(d), PBE1PBE/aug-cc-PVTZ//PBE1PBE/6-311+G(d,p) and CBS-QB3 series led to MAD equal to 0.9kcalmol−1 and R2>0.9997. As well, the acidity/basicity values of compounds in aqueous phase were computed using obtained solvation free energies with SM8 and CPCM solvation models successfully. Three reliable series containing PBE1PBE/aug-cc-PVTZ//PBE1PBE/6-31+G(d), PBE1PBE/aug-cc-PVTZ//PBE1PBE/6-311+G(d,p) and CBS-QB3 series led to MAD equal to 1.0, 1.0 and 0.8 pKa unit, respectively. Moreover, gas phase acidity/basicity and pKa values of some fluorinated compounds were predicted using purposed reliable methods.