Room-temperature changes in the structure of a new diisopropylammonium chloride (C6H16ClN, DIPAC) molecular ferroelectric have been investigated by high-resolution cross polarization/magic-angle spinning nuclear magnetic resonance (CP/MAS NMR) and X-ray diffraction (XRD) methods. The NMR measurements are carried out using 13C nuclei. Depending on time and heat treatment, monoclinic ferroelectric or orthorhombic nonpolar phases (as well as their coexistence) are observed. It is shown that the polar DIPAC modification at room temperature is transformed in the course of time into the nonpolar orthorhombic structure.