Application of the Modified Urey–Bradley–Shimanouchi Force field of α-D-Glucopyranose and β-D-Fructopyranose to Predict the Vibrational Spectra of Disaccharides

The vibrational frequencies of the disaccharide isomaltulose in the solid state have been reproduced in the 50–4000 cm⁻¹ range. The modified Urey–Bradley–Shimanouchi force field was used, combined with an inter molecular potential energy function that includes van der Waals interactions, electrostatic terms, and an explicit hydrogen bond function. The force constants previously established for α-D-glucopyranose and β-D-fructo pyranose, as well as the crystallographic data of isomaltulose monohydrate, were the starting parameters for the present work. The vibrational frequencies of isomaltulose were calculated and assigned to the experimentally observed vibrational frequencies. Overall, there was good agreement between the observed and calculated frequencies with an average error of 4 cm⁻¹. Furthermore, good agreement was found between our calculated results and the vibration spectra of other disaccharides and monosaccharides.