Relative stability of 1C4 and 4C1 chair forms of β-d-glucose: a density functional study

The method and basis set dependence of the relative energies of the 1C4 and 4C1 chair forms of β-d-glucose were calculated for two selected, low-energy hydroxyl rotamers at various levels of generalized gradient approximation density functional theory (GGA-DFT). The GGA-DFT and MP2 methods provide similar energetic differences for β-d-glucose conformers. Addition of the diffuse functions to a double-zeta quality basis set and inclusion of the HF exchange into the DFT functionals improve the agreement between the DFT and the best composite estimates of the energetic differences. The GGA- or hybrid-DFT methods reproduce the geometrical consequences of correlation effects correctly for glucose.