<i>Ab Initio</i> computed molecular structures and energies of the conformers of glucose

Abstract

Abstract Ab initio computations indicate the existence of several stable and some unstable conformers in isolated α and β glucose molecules. All of the lower‐energy conformers exhibit a strikingly regular pattern of internal hydrogen bonding. Five such stable structures have been identified for each of the α and β anomers, differing primarily in the orientation of the CH 2 OH group. In each conformer, the α anomer is predicted to be lower in energy than the corresponding conformers of β anomer. The difference is about 2 kcal/mol in the 4‐31G basis but only 0.4 kcal/mol in the 6‐31G* basis. It is found that the electronic contributions to the free energy difference stabilize the α anomer while the nuclear motion contributions stabilize the β anomer. The implications of these predictions and the future investigations required to understand the relative stabilities of the two anomers are pointed out. © 1992 by John Wiley &amp; Sons, Inc.