The paper presents the results of new attenuated total reflectance infrared (ATR-IR) spectroscopic studies and Car-Parrinello molecular dynamics (CPMD) simulations of phosphorous acid (H3PO3)–N,N-dimethylformamide (DMF) mixtures over the whole composition range. The above results were analyzed to find out the dependence of the solutions` structure on their concentrations. These newly obtained data were studied along with the similar data for phosphoric acid (H3PO4) solutions in DMF published by us earlier. The experimental (ATR) and calculated (CPMD) data on the geometrical parameters and topology of H-bonds, as well as on the energy of the proton transfer in H3PO3–DMF and H3PO4–DMF solutions were analyzed jointly. The paper also discusses changes in the solutions' structure depending on the structure of the original acids.
