INFRARED STUDY ON THE DOUBLE HYDROGEN-BOND BETWEEN THE UREA MOLECULE AND HALOGENATED ALIPHATIC HYDROCARBON SOLVENTS

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.