Monosaccharides 1-5, which differ in configuration at C1 and/or C2, were chosen to determine whether DFT can be used to calculate accurate 1 J CC values in diverse structures. In 1-5, rotation of the C1-C2 bond, which affects 1 J C1,C2 , is constrained by the aldohexopyranosyl rings, which highly prefer 4 C 1 chair conformations in each case. Thus, only rotations about the C1-O1 and C2-O2 bonds influence 1 J C1,C2 values in solution (neglecting intermolecular factors such as hydrogen bonding). In crystalline 1-5, the latter rotations are constrained by the lattice, and X-ray structures provide these angles with reasonably high accuracy (±4 o ). Crystalline compounds, doubly C-labeled, can be used to measure J CC values by solid-state C NMR. Since the relevant C-C and C-O torsion angles can be determined from the X-ray crystal structures, appropriate in silico models of each compound can be built from which J CC values can be calculated and compared to experimental values.