Intermolecular hydrogen bonding interactions of furan, isoxazole and oxazole with water

Intermolecular hydrogen bonding between furan, isoxazole, oxazole and water has been analysed using theoretical methods. Ab initio and DFT methods have been employed to optimize the adducts of heterocycles with single water molecule. The stabilization energies associated with the adduct formation are evaluated at B3LYP/AUG-cc-pVDZ//B3LYP/6-31+G∗, MP2/AUG-cc-pVDZ//MP2/6-31+G∗ levels and corrected for zero-point vibrational energies (ZPE) and basis set superposition error (BSSE) using counterpoise method. Natural bond orbital analysis (NBO) at MP2/6-31+G∗ has also been carried out to study electron delocalization of these adducts. The hydrogen bond acceptor ability of heteroatoms and π cloud of the ring are compared. In the heterocyclic molecules with nitrogen and chalogen in 1, 2 and 1, 3 positions, the nitrogen is better hydrogen bond acceptor than the chalcogen in all cases.