Stable conformers of glucopyranose in the gas-phase have their vicinal hydroxyl groups arranged in an apparent O-A-H-D...O-A acceptor-donor-acceptor sequence. Notwithstanding this, there is no evidence of intramolecular hydrogen bonding based oil the absence of (3, -1) bond critical points between the putative donors and acceptors. Moreover, these hydroxy groups show negative cooperativity (synergy) based on changes in O-H bond length, sigma* antibonding orbital occupancies, orbital overlap integrals, and IR blue-shifts compared to ethane-1,2-diol, rather than positive cooperativity as would be expected if intramolecular hydrogen bonding was present, suggesting that this interaction is on balance repulsive rather than attractive. (c) 2006 Elsevier B.V. All rights reserved.