The structure of 5,5-bis(bromomethyl)-2-phenyl-1,3-dioxane was investigated by the methods of 1Н, 13С NMR spectroscopy and X-ray analysis. The molecule exists in the chair conformation with the equatorial phenyl group. The routes of interconversion of the ring, free conformational energy and optimal conformation of the phenyl group were determined using computer modeling by the method of DFT (PBE/3ξ). The results are consistent with the data of X-ray analysis. © 2018, Pleiades Publishing, Ltd.