Hydrogen Bonding Interaction between Ureas or Thioureas and Carbonyl Compounds

The hydrogen bonding interactions between ureas or thioureas and different carbonyl compounds were studied using the Moller-Plesset perturbation theory (MP2). The natural bond orbital analysis further disclosed the essence of the hydrogen bonding interaction. In addition, the substituent effects were investigated and the results indicated that both the electron-withdrawing groups on ureas (thioureas) and electron-donating groups on carbonyl compounds can facilitate the hydrogen bonding formation. Two possible hydrogen bonding complex conformations, cis and trans, were discussed and the energy gaps between them were analyzed, in combination with the catalytic reactions.