This research article published by Science Publishing Group, 2015Glucosamine and acetylglucosamine are the constituents of chitosan and chitin natural biopolymers. In the present study, the structure and properties of the D-glucosamine monomer (A), N-acetylglucosamine monomer (B), and ion-molecular adducts with Na+ cation have been explored. The equilibrium geometrical structure, vibrational spectra of the species have been determined, using the DFT/B3LYP method with the 6-31G(d) basis set. Larger basis sets up to 6-311++G(d,p) were utilized to compute energies of reactions between Na+ ion and A and B molecules. The exothermicity and spontaneous character of the adducts formation reactions have been confirmed.