Interactions of Hydroxyurea with a Water Molecule. Ab Initio Molecular Orbital Study

Abstract

Ab initio quantum chemical studies at the HF and MP2 levels with the 6-31G** basis set were performed for hydrogen-bonded complexes of hydroxyurea with a water molecule (HUW). Since at both the HF and MP2 levels of theory the keto forms of both E and Z tautomers of hydroxyurea are found to be much more stable compared to iminol forms, only keto forms were included in our study of HUW. The interaction energies were corrected for the basis set superposition error (BSSE) by using the full Boys−Bernardi counterpoise correction scheme. The zero-point vibrational energies are calculated at the MP2/6-31G**//MP2/6-31G** level. In addition, single-point calculations were performed at the MP2/6-311++G(2df,2pd)//MP2/6-31G** and at the CCSD(T)/6-31G**//MP2/6-31G** levels of theory. It was shown that the complex I of HUW is the global minimum on the potential energy surface and also has the largest interaction energy. On the basis of the results of these calculations, the stability of the different conformers of HUW, the nature of the specific hydrogen-bonding interactions, and the interaction energies are discussed.

The Nitric Oxide Producing Reactions of Hydroxyurea

“…In addition, these studies show that hydroxyurea primarily adopts the keto form in which the hydroxyl group orients itself anti to the carbonyl group and forms a hydrogen bond to the carbonyl group of a neighboring molecule. A group of recent theoretical studies also indicate that the keto form is significantly more stable than the imino forms (>10 kcal/mol) with the anti keto form being more stable than the syn by 3.7 kcal/mol [27][28][29][30]. A series of infrared spectroscopic experiments however suggest that the imino forms may be favored in different solvents [31][32][33][34].…”

Isomerical and structural determination of N-hydroxyurea: a matrix isolation and theoretical study

“…Theoretical studies of the HU structure were performed at different theory levels. HF and MP2 calculations with the 6-31**G basis set 38,39 as well as the DFT study 40 indicate that the keto (hydroxamic) forms are substantially more stable (about 40-85 kJ mol À1 ) than the iminol (hydroximic) tautomers. The higher stability of the keto form of HU is mainly caused by electronic factors and mostly related to the exceptional stability of the carbonyl group.…”

Hydrogen-bonded complexes of acetylene and acetonitrile: A matrix isolation infrared and computational study

“…Studies of hydrogen-bonded complexes, both experimental and theoretical, are of considerable interest [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The conventional hydrogen bond (H-Bond) where an XAH bond interacts with Y is represented by XAHÁ Á ÁY.…”