Structure and Conformational Analysis of 5,5-Bis(bromomethyl)-2,2-diphenyl-1,3-dioxane

The structure of 5,5-bis(bromomethyl)-2,2-diphenyl-1,3-dioxane was studied by 1 H and 13 C NMR spectroscopy and X-ray analysis. Its molecules in crystal adopt a chair conformation, whereas equilibrium between energy-degenerate chair invertomers exists in solution at room temperature. According to the low-temperature NMR data, the interconversion barrier amounts to 8.9 kcal/mol. The ring inversion path was simulated by DFT quantum chemical calculations using PBE/3ξ and (in some cases) RI-MP2/λ2 approximations, and the potential barrier to interconversion in different solvents was estimated by the cluster model. The calculated geometric parameters of the title compound were consistent with the experimental X-ray diffraction data, and the calculated interconversion barrier matched a cluster containing 5 molecules of methylene chloride in the nearest solvation shell of the substituted 1,3-dioxane molecule.