Herein, employing density functional theory (DFT) and handling the solvent effects with the PCM model, the structural parameters, energy behavior, natural bond orbital analysis (NBO), as well as the tautomerism of Felbamate are investigated. <...> F1 is the kinetically and thermodynamically most stable tautomer of Felbamate, which contains the amide group in each of the carbamate moieties. <...> The calculated NMR chemical shifts and IR vibrational frequencies are in good agreement with the experimental values, confirming the suitability of the optimized geometry for Felbamate. <...> The tautomerization reaction of F1 to each of the other tautomers occurs via an intramolecular proton transfer. <...> This reaction affects considerably the structural parameters and atomic charges of the Felbamate molecule. <...> A large HOMO-LUMO energy gap implies a high stability of the F1 tautomer. <...> INTRODUCTION Felbamate (FBM, Taloxa) or 2-phenyl-1,3-propanediol dicarbamate is a new antiepileptic drug that was marketed under the brand name Felbatol by MedPointe in 1993. <...> Nowadays, DFT is widely employed in many areas of computational chemistry, such as geometry optimizations, spectroscopic assignments, investigations of the reaction kinetics and mechanisms, drug science, and so on [10—14 ]. <...> In this work, we address this issue and examine its molecular geometry, tautomerism, vibrational frequencies, NMR chemical shifts, and the natural bond orbital (NBO) analysis using valuable DFT approaches. <...> THEORETICAL All of the present calculations have been performed with the Gaussian 03 software package [ 15 ] using the B3LYP [ 16 ] functional and the 6-311+G(d,p) basis set. <...> For the investigation of solvent ef© Khaleghi-Rad A., Beyramabadi S.A., Morsali A., Ebrahimi M., Khorasandi-Chenarboo M., 2017 262 A. KHALEGHI-RAD, S.A. BEYRAMABADI, A. MORSALI ET AL. fects in an aqueous solution, one of the self-consistent reaction field methods, the sophisticated polarized continuum model (PCM) [ 17 ] has been employed. <...> The optimized geometries were confirmed to have no imaginary frequency, except for the transition state (TS) that has only one imaginary frequency of the Hessian. <...> The zero-point corrections and thermal corrections have been considered in evaluation of the energies. <...> The optimized geometry was used to compute the vibrational frequencies, NMR chemical shifts, atomic charges, and the NBO analysis. <...> The Felbamate drug <...>