Jc. Dobrowolski et al., INFRARED STUDY ON THE DOUBLE HYDROGEN-BOND BETWEEN THE UREA MOLECULE AND HALOGENATED ALIPHATIC HYDROCARBON SOLVENTS, Vibrational spectroscopy, 8(1), 1994, pp. 53-60
The infrared bands of C=O and N-H stretching vibrations of urea dissol
ved in a series of halogen derivatives of aliphatic hydrocarbons were
analyzed. From the relationship between the solubility of urea and the
structure of the solvent as well as the infrared spectra it is conclu
ded that a double hydrogen bond between one urea and one solvent molec
ule is formed. In this bond, the solvent molecule is donor of two hydr
ogen atoms of two polar C-H bonds, and the C=O group of urea is proton
acceptor. The interaction of N-H groups with X-C solvent groups is pr
edominantly determined by the valence orbital repulsion of N and X ato
ms, and the polarizability of the halogen atom X.