Submitted to: Midwest Theoretical Chemistry Conference
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2008
Publication Date: June 28, 2008
Citation: Bosma, W.B., Schnupf, U., Willett, J.L., Momany, F.A. 2008. Distinguishing Between Monosaccharides Using Infrared Spectroscopy: DFT Calculations on Glucose and its Epimers. Midwest Theoretical Chemistry Conference. xx. Technical Abstract: Glucose and each of its seven epimers were geometry-optimized at the B3LYP/6-311++G** level of theory, both in vacuo and with the COSMO solvation method. Several different conformations of each anomer were examined for every epimer, with all possible combinations of hydroxymethyl rotamers (gg, gt, or tg) and hydroxyl orientation (clockwise or counter-clockwise). The infrared spectra were calculated for several low-energy structures of each epimer, and the different conformer spectra were averaged with the appropriate weighting factors. It was found that the in vacuo epimers gave fairly distinct infrared spectra, which could, in principle, be used to distinguish them. The implicit solvent model caused some redshifting of the peaks relative to the vacuum structures, without causing much change to the nature of the vibrations themselves. By contrast, a glucose molecule complexed with five explicit water molecules showed an infrared spectrum that was very similar to the vacuum in the 900-1500 cm'1 region, but very different from the vacuum glucose in the OH stretch region. In addition, the nature of the vibrational motions responsible for the infrared peaks were altered considerably by the presence of the explicit water molecules.