Rearrangement of hydrogen bonds in dehydrated raffinose tetrahydrate: a time‐of‐flight neutron diffraction study

• Published in: Acta crystallographica. Section C, Crystal structure communications Crystal structure communications, 2022-12, Vol.78 (12), p.743-748
• Main Authors: Kawasaki, Takuro, Takahashi, Miwako, Kiyanagi, Ryoji, Ohhara, Takashi
• Format: Article
• Language: English
• Subjects: Bonding strength; Chemical bonds; Crystal structure; Crystals; Dehydration; Hydrogen; hydrogen bonding; Hydrogen bonds; Lattice parameters; Neutron diffraction; Raffinose; raffinose hydrate; time‐of‐flight; Water chemistry
• ISSN: 2053-2296; 0108-2701; 2053-2296; 1600-5759
• DOI: 10.1107/S2053229622010828

Structural changes of the raffinose crystal on dehydration from the pentahydrate to the tetrahydrate were investigated by single‐crystal time‐of‐flight neutron diffraction. It was revealed that during the dehydration, rearrangement occurs in the hydrogen bonds related to the lost water molecule, while the symmetry of the crystal structure is retained. The hydrogen‐bonding status of raffinose pentahydrate and tetrahydrate were discussed comprehensively according to Jeffrey's hydrogen‐bonding classification. It was shown that the water molecules are hydrogen bonded to the surrounding molecules by moderate O—H…O hydrogen bonds and weak C—H…O hydrogen bonds, and the number of these two types of hydrogen bonds determines the water molecules that are removed by dehydration. The lattice constant c showed a significant decrease on dehydration and further dehydration leads to loss of crystallinity of the raffinose crystals. The geometry of hydrogen bonds in raffinose pentahydrate and dehydrated tetrahydrate single crystals was studied by time‐of‐flight neutron diffraction. The rearrangement of water molecules and the decrease in lattice constant c during dehydration were demonstrated.