This research has focused on the chemical reactivity behavior of favipiravir forms and transition states of forms. These compounds are potential drugs for the Ebola virus and have shown its effectiveness for COVID-19. Geometry optimizations have been conducted by using the DFT method with the B3LYP/6-311G(d,p) method in the gas phase and 4 different solvent environments. Polarized Continuum Model has been used to evaluate the solvent effect on chemical stability and its related properties. Dipole moment, polarizability, and molecular first-order hyperpolarizability of the favipiravir forms were computed for gas and solvent phase. Also, thermodynamic properties such as heat capacity, entropy, and enthalpy of the A3 form of favipiravir at different temperatures were calculated in the gas phase.