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Obtained results show that solvation energies are not significantly different between DFT methods using the numerical (DNP) and Gaussian basis set (aug-cc-pVTZ). It is noteworthy that the independent and suitable solvation energy of proton of -258.6 kcal/mol has been proposed for the evaluation of pKa values in conjunction with the numerical basis set. In addition, the calculated pKa values suggest that the anti-conformation of 5-formyluracil is the most stable form in the aqueous solution. | Vietnam Journal of Science and Technology 55 (6A) (2017) 63-71 THEORETICAL EVALUATION OF THE pKa VALUES OF 5-SUBSTITUED URACIL DERIVATIVES Pham Le Nhan1, *, Nguyen Tien Trung2 1 Faculty of Chemistry, University of Dalat, 01 PhuDong Thien Vuong,Ward 8, Dalat, Viet Nam 2 Chemistry Department and Laboratory of Computational Chemistry and Modelling, Quy Nhon University, 170 An Duong Vuong, Quy Nhon, Viet Nam Email: nhanpl@dlu.edu.vn; nguyentientrung@qnu.edu.vn Revised: 15 July 2017; Accepted for publication 21 December 2017 ABSTRACT Density functional theory (DFT) calculations using numerical basis sets were employed to predict the solvation energies, Gibbs free energies and pK a values of a series of 5-substituted uracil derivatives. Obtained results show that solvation energies are not significantly different between DFT methods using the numerical (DNP) and Gaussian basis set (aug-cc-pVTZ). It is noteworthy that the independent and suitable solvation energy of proton of -258.6 kcal/mol has been proposed for the evaluation of pKa values in conjunction with the numerical basis set. In addition, the calculated pKa values suggest that the anti-conformation of 5-formyluracil is the most stable form in the aqueous solution. Keywords: numerical basis sets, Gaussian basis sets, pKa values, solvation energies, uracil. 1. INTRODUCTION There are different types of one-electron basis sets in computational chemistry including the Slater, Gaussian, numerical basis sets and others. Unlike Gaussian basis sets, numerical basis sets include basis functions which are generated numerically from the nucleus to an outer distance of 10 a.u. of each atom. Actually these functions have two parts involving spherical harmonic functions Ylm(θ,φ) as angular portions and radial functions F(r). Values of radial portions are obtained by numerically solving the atomic DFT equations [1]. Numerical basis sets have plenty of advantages in comparison to Gaussian ones and other analytical functions .
