A computational study of conformers and rotamers of 3-substituted equatorial tetrahydro-2H-thiopyran-1-oxides (tetrahydrothiopyran-1-oxides, thiacyclohexane-1-oxides, thiane-1-oxides)

Ab initio molecular orbital theory with the 6-31G(d), 6-31 + G(d), 6-31G(d,p), and 6-31G(2d) basis sets has been used to calculate the geometry optimized structures and the relative energies (DeltaE) of the rotamers of the chair conformers of 3substituted equatorial tetrahydro-2H-thiopyran-1-oxides (tetrahydrothiopyran-1-oxides, thiacyclohexane-1-oxides, thiane-1-oxides; CH3, CF3, CHO, COCH3, CN, F, Cl, Br). The conformational free energies (DeltaG degrees) and relative energies (DeltaE) of the conformers and rotamers are discussed in terms of the repulsive nonbonded interactions in both conformers. (C) 2001 Elsevier Science B.V. All rights reserved.