1. The normal coordinate analysis of urea, thiourea, and thier isotopic analogues in the solid phase and in solution
- Author
-
J. Kidrič, B. Barlič, Ž.V. Kneževic, and D. Hadži
- Subjects
chemistry.chemical_compound ,chemistry ,Thiourea ,Computational chemistry ,Hydrogen bond ,Selenourea ,General Engineering ,Urea ,Physical chemistry ,Molecule ,Potential energy ,Spectral line ,Matrix method - Abstract
The i.r. spectra of solid and in CH3CN dissolved normal urea and thiourea, their 15N and 2H isotopic species, and solid selenourea-D4 were recorded. The normal coordinate analysis of 13 in-plane vibrations of these molecules, including the in-plane vibrations of urea-18O assigned by Laulicht [1] has been made using Wilson's GF matrix method and the Urey Bradley force field. The Urey—Bradley force field reproduces well the heavy istope frequency shifts. Several sets of force constants have been calculated and their validity is discussed in terms of other bond characteristics. The values of KCN force constants increase in this order of urea, thiourea and selenourea. The frequency shifts and the differences in the force constants of ureas and thioureas in the solid phase and in solution show that hydrogen bonding strongly affects the potential energy distribution, specially for the CO stretching mode.
- Published
- 1976