The global internal rotation potentials of methanediol, methanediamine, and aminomethanol have been obtained at the MP2/6-311 + g(2d,p) level by scanning through the dihedral angles of the two functional groups with the remaining nuclear coordinates being energy-minimized at the MP2/6-31G ∗∗ level. The intramolecular hydrogen bonding between the two functional groups is represented by the general functional forms of the electric dipole-dipole, dipolequadrupole, and quadrupole-quadrupole interactions. The through-direct-bond potentials between the functional group and its adjacent CH 2O or CH 2N molecular fragment are represented by the conventional three Fourier terms. It is found that the global conformational potentials of these molecules can be adequately represented by the general functional forms of these two types of potentials. The obtained electrostatic interaction strengths are in good agreement with the predictions of the theoretical local dipole and quadrupole moments of the functional groups calculated by the Hirshfeld charge population analysis. The present energy-decomposition analysis suggests that both the electrostatic interactions and the charge-delocalization interaction of the lone-pair electrons of either oxygen or nitrogen atom to its adjacent molecular fragment are equally important in determining the global conformational potentials. It also suggests that the origin of the anomeric effect of these compounds can be quantitatively explained in terms of these interactions. The relationship between the present energy-decomposition analysis and the other proposed interaction models for the anomeric and exo-anomeric effects is discussed.