Solid state NMR and X-ray diffraction studies of α-d-galacturonic acid monohydrate Original Research Article

Crystalline α-d-galacturonic acid monohydrate has been studied by 13C CPMAS NMR and X-ray crystallography. The molecular dynamics were investigated by evaluating 13C spin-lattice relaxation in the rotating frame (T1ρ) and chemical-shift-anisotropy properties of each carbon. Only limited molecular motions can be detected in the low frequency (<104 Hz) range by 13C relaxation time measurements (T1ρ) and changes of chemical shift anisotropy properties as a function of temperature. X-ray analysis (at both ambient temperature and 150 K) shows that the acid has the usual chair-shaped, pyranose ring conformation, and that the acid and water molecules are linked, through all their OH groups, in an extensively hydrogen-bonded lattice.