This paper presents the results of experimental studies of hydrogen-bonded 2-pyridone crystal IR spectra. Spectral studies have demonstrated the existence of two anhydrous solid-state phases of each compound, namely the alpha and the beta phases. Hydrogen bonds in the high-temperature alpha phase of these crystals have been estimated to be 40% stronger than the hydrogen bonds in the beta phase, which are stable at room temperature. The mechanism of the phase transition in the solid-state 2-pyridone is proposed on the basis of the IR spectral data. This was possible by taking into account small changes in the geometry of heterocyclic molecular skeletons, which accompany the electron density redistribution in the hydrogen bonds occurring during the transition. The phase transition is connected with a partial change in the hydrogen bond nature from the N+-H center dot center dot center dot O- in the alpha phase, to the N-H center dot center dot center dot O hydrogen bonds in the beta phase crystals.