Intermolecular interactions in crystals of small unsubstituted cyclic ethers and substituted epoxides

CE-B3LYP model energies are used to investigate intermolecular interactions in crystals of the relatively weakly bound cyclic ethers, as well as a number of substituted epoxides that have been the focus of high-quality experimental electron density studies. This approach readily provides a complete picture of all intermolecular interactions in these molecular crystals, and CE-B3LYP lattice energies for the unsubstituted cyclic ethers are in excellent agreement with available thermodynamic data. When compared with the outcomes of multipole modelling of X-ray diffraction data, these results suggest that experimental interaction energies are typically underestimated and, contrarily, experimental lattice energies are typically overestimated. These observations deserve careful investigation.