On hydrogen bonding in 1,6‐anhydro‐β‐ d ‐glucopyranose (levoglucosan): X‐ray and neutron diffraction and DFT study

The geometry of hydrogen bonds in 1,6‐anhydro‐β‐ d ‐glucopyranose (levoglucosan) is accurately determined by refinement of time‐of‐flight neutron single‐crystal diffraction data. Molecules of levoglucosan are held together by a hydrogen‐bond array formed by a combination of strong O—H⋯O and supporting weaker C—H⋯O bonds. These are fully and accurately detailed by the neutron diffraction study. The strong hydrogen bonds link molecules in finite chains, with hydroxyl O atoms acting as both donors and acceptors of hydroxyl H atoms. A comparison of molecular and solid‐state DFT calculations predicts red shifts of O—H and associated blue shifts of C—H stretching frequencies due to the formation of hydrogen bonds in this system.