| TUD Organische Chemie | | Immel | | Publications | | Papers | | Abstract 27 | | | View or Print (this frame only) |
T. Nakagawa, S. Immel, F. W. Lichtenthaler, and H. J. Lindner
Carbohydr. Res. 2000, 324, 141-146.
Dissolution of α-cyclodextrin (α-CD) in 9:1 water-nitromethane smoothly generates the title compound, which crystallizes as the pentahydrate in the orthorhombic space group P212121 with a = 9.452(4), b = 14.299(3), c = 37.380(10) Å, and Z = 4. Its crystal structure analysis revealed the α-CD macrocycle in an unstrained conformation stabilized through a ring of O-2 ... O-3' hydrogen bonds between five of the six adjacent glucose residues. The nitromethane is located in the α-CD cavity in an orientation parallel to the plane of the macrocycle, and assumes two sites of equal population with the nitro group in excessive thermal motion; the guest is held by van der Waals contacts and C-H ... O-type hydrogen bonds to the pyranose H-3 and H-5 protons. The packing of the macrocycles in the crystal lattice is of cage herringbone-type with an extensive intra- and intermolecular hydrogen bonding network. The ready formation of a nitromethane inclusion complex in aqueous nitromethane, and the subtleties of its molecular structure amply demonstrate the ease with which water is expelled from the α-CD cavity by a more hydrophobic co-solvent.
Additional Graphics: Cyclodextrin Inclusion Complexes