CHEMICAL-STRUCTURE OF UREA IN WATER

Urea, urea dimer, and the complexes of urea and water molecules were s tudied using density functional theory. A hydrogen-bonded, cyclic urea dimer was found to be the most stable conformation. Its binding energ y, 10.9 kcal/mol, was obtained using a gradient-corrected density func tional approach. The conformations of minimum energy isomers of urea w ith water molecules were also determined. The stability of the urea di mer in solution was investigated by systematically increasing the numb er of the water molecules in the system. Our results indicate that, du e to hydrogen bonding between urea and water, the urea dimer would be unstable and would separate into monomers when the number of water mol ecules becomes sufficiently large.