Solvation Studies of Glucose

D-Glucose is the most ubiquitous carbohydrate in nature, found in table sugar, starch, and cellulose. Its broad array of configurations and conformations 

As with any saturated six-member ring, the ring-flip process interconverts two-chair conformations. For D-glncose, these chair conformations are designated for 6 (also for 7) and 4 for its ring-flipped conformer 10. Introdnctory organic chemistry texts instruct us that equatorial substitution is favored over axial, and therefore, 6 is more stable than In fact, little computational work 

Since almost no furanose form of D-glucose is observed in solution, it is expected that the energies of the furanose conformational isomers will be much greater than those of the pyranose form. In fact, the four furanose isomers examined are predicted to be about 4-5 kcal mol higher than the lowest pyranose conformers 6a and 6c at HF/6-31G. Quite remarkable, however, was the B3LYP/6-31G  

TABLE 7.10 Computed Relative Energies (in kcal mol of n-Glucose Configurations  

Much of the computational literature of glucose pertains to the ratio of the two anomers. This is formulated as the anomeric effect the stability of the a anomer, with its axial group, over the expectedly more stable p anomer, where the hydroxyl group occupies the equatorial position. This has been rationalized in two ways (1) minimizing the dipole-dipole repulsion because of the C-O bonds or (2) hyperconjugative stabilization by donation of the ring oxygen lone pair 

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