The crystal structure of α-D-glucose monohydrate

Abstract

& Boyd (1971). Further inspection of Fig. 2 suggests that the structure initially induced by the transition at 4800 kg cm -2 is not stable within the time scale of the X-ray exposure. For example the spacing of the (110) plane of the tetragonal structure at 4800 kg cm -2 still shows a little expansion with a further increase in pressure of 100 kg cm -2, as compared with Fig. 1, where steady reduction of the (110) spacing is seen above 5000 kg cm -2. In all these pressure regions, the (011) and (002) planes show steady decrease in spacing with increasing pressure and are more compressible than the (110) plane. Thus the crystal of adamantane after the transition is fairly anisotropic in the strains induced by hydrostatic pressures, being more compressible in the c direction than in the directions perpendicular to it. The strains are, however, isotropic before the transition, as shown by the cubic structure sustained under pressure (Fig. 1). The unit-cell dimension of the cubic structure just before the pressure transition is a= 9.20 A (at 4600 kg cm -2) and the calculated volumetric strain of the crystal at this stage is 6"9 %.It is worth while to note that at p, and 20°C, the crystal transition in adamantane arises in such a way that one of the original cubic axes shrinks 4.2 % and becomes parallel to the tetragonal c axis, while both of the other two axes expand 0.5% in the tetragonal [110] and [110] directions (numerical values were calculated at two pressures, 4600 and 5000 kg cm-2). The net effect is an abrapt volumetric contraction of 3-1%, which corresponds to abrupt molecular rearrangements toward denser packing.

Microwave Spectroscopy of Biomolecular Building Blocks

“…60 , À60 or 180 , respectively. Experimental observations in both the solid phase [211,[214][215][216][217]254] and solution [212,213,233] display approximately equal populations of G+ and GÀ conformers, with an almost complete absence of the T conformer. This propensity in glucopyranosides to adopt gauche conformations is known as gauche effect [255, 256 and references therein].…”

“…Numerous experimental studies on α-and β-glucopyranosides, both in solid [211,[214][215][216][217]254] and solution phases [262][263][264], have shown that the dihedral angle (O 6 -C 6 -C 5 -O 5 ) displays a preference for GÀ and G+ gauche configurations, which has been attributed to the gauche effect [255]. This feature was exemplified in a statistical analysis of X-ray structures of glucopyranosyl derivatives [265], yielding a rotamer population of 40:0:60 (G+/T/GÀ).…”

Measurement and calculation of 13C chemical shift tensors in α-glucose and α-glucose monohydrate

“…Comparison of the principal components (s11, s22, s33) of the chemical shielding tensors for each carbon site calculated using CASTEP with the principal components (d11, d22, d33) of the chemical shift tensors measured experimentally from the spinning sideband manifolds in slow MAS spectra. The chemical shielding tensors in a and b were calculated from the published X-ray diffraction structure of a-glucose·H2O 36 errors in the quantum chemical calculation method itself, related to the calculation of the paramagnetic contribution to the chemical shielding, which stem from the fact that it is difficult for existing exchange-correlation functionals to reproduce dynamic polarization in low electron density regions. 48 Nonetheless, with an appropriate calibration curve that relates chemical shieldings and chemical shifts, highly accurate calculations of chemical shift tensors can be still be performed.…”

Factors controlling relative stability of anomers and hydroxymethyl conformers of glucopyranose

“…There are three different crystal structures available for glucose, two conformers, 5 75 and 8, 76 solved by x-ray diffraction, and one conformer, 7,…”