Crystal and molecular structures of glycolide and lactide: Association through CH center dot center dot center dot O hydrogen bonds

The X-ray crystal structures of glycolide (1,4-dioxane-2,5-dione) and L(-)- and DL-lactide (3,6-dimethyl-1,4-dioxane-2,5-dione) are reported. The geometric parameters of the molecules which have flattened boat conformations, were determined. Short intermolecular H...O distances 2.3-2.4 Angstrom between the methylene and carbonyl groups are considered as hydrogen bonds. This interpretation is supported by spectroscopic data and quantum-chemical calculations.