| Autor: |
Hünig, Isabel, Painter, Alexander J., Jockusch, Rebecca A., Çarçabal, Pierre, Marzluff, Elaine M., Snoek, Lavina C., Gamblin, David P., Davis, Benjamin G., Simons, John P. |
| Zdroj: |
Physical Chemistry Chemical Physics (PCCP); 2005, Vol. 7 Issue: 12 p2474-2480, 7p |
| Abstrakt: |
The gas phase structures of phenyl α- and β-d-xylopyranoside α- and β-pXyl and their mono-hydrates have been investigated using a combination of resonant two-photon ionization R2PI, ultra-violet hole-burning and resonant infrared ion dip spectroscopy, coupled with density functional theory DFT and ab initiocomputation. The hole-burning experiments indicate the population of a single conformer only, in each of the two anomers. Their experimental and calculated infrared spectra are both consistent with a conformational assignment corresponding to the computed global minimum configuration. All three OH groups are oriented towards the oxygen atom O1 on the anomeric carbon atom to form an all transttt counter-clockwise chain of hydrogen bonds. The mono-hydrates, α- and β-pXylH2O each populate two distinct structures in the molecular beam environment, with the water molecule inserted between OH4 and OH3 or between OH3 and OH2 in α-pXylH2O, and between OH2 and O1 in either of two alternative orientations, in β-pXylH2O. In all of the mono-hydrated xyloside complexes, the water molecule inserts into the weakest link of the sugar molecules’ hydrogen-bonded chain of hydroxy groups, creating a single extended chain, strengthened by co-operativity. The all-transconfiguration of the xylose moiety is retained and the mono-hydrate structures correspond to those calculated to lie at the lowest relative energies. |
| Databáze: |
Supplemental Index |
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