Complete vibrational assignments have been performed for free base, cationic and hydrochloride species derived from antiviral adamantadine by combination of hybrid B3LYP with the 6-31G* and 6-311++G** basis sets and the SQMFF methodology. Normal internal coordinates and scaling factors were used to obtain the harmonic force fields and scaled force constants of three species in gas phase and in aqueous solution. Bond lengths and angles of cationic and hydrochloride species show very good concordances with the experimental of amantadinium azide. The cationic species reveals higher solvation energy value, as compared with antiviral agents, however, brincidofovir, the antiviral used to ebola disease presents a higher reactivity against to adamantadine. Positive value of Mulliken charge on N1 of hydrochloride species in solution could justify the ionic character of H29•••Cl30 bond, as evidenced by bond order and AIM calculations. The hydrochloride species is the most reactive in both media while the cationic species the less reactive. High electrophilicity and nucleophilicity indexes of cationic species in both media justify its higher hydration. Good concordances were observed between experimental and predicted 1H and 13C NMR and electronic spectra. In solution, the three species are present as revealed by the experimental UV spectrum of hydrochloride amantadine