In order to better evaluate the contributors to the conformational energy of D-glucopyranose, the geometry-energy relationships for a sequence of model compounds were determined. The conformational energies of 1-hydroxy 3-hydroxymethylcyclohexane and 2-hydroxy 6-hydroxymethyltetrahydro-<i>2H-</i>pyran were used to model D-glucopyranose. The conformational energies were determined at the B3LYP/6-311G++(d,p) and MP2/6-311++(d,p) levels in the gas phase and solution. The relative B3LYP energy as a function of the orientation of the substituents were determined by relaxed scans as the –CH<sub>2</sub>-OH at C5 was rotated about the OCCO and HOCC dihedrals and the –OH at C1 was rotated about the HOCO dihedral. The lowest energy rotamers for the axial (α) and equatorial (β) conformers were used to calculate the conformational energy. Because solute-solvent interactions have significant effects on the relative stability of the axial and equatorial conformers, the energy versus dihedral scans were repeated using a continuum solvent model with water (ε = ~80), acetone (ε = ~20) and cyclohexane (ε = ~2) selected as the solvent.

Computational study of the contributions to the relative stability of the α and β conformers of D-glucopyranose

249th National Meeting (2015)

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