Table 3.
Predicted frequencies of νas(CN) band of urea in combination with water or other urea molecules. Calculations were performed using Gaussian 09.29 Where larger urea ensembles were modeled, only the frequencies of those ureas with the highest number of H-bonds to their carbonyl oxygen are listed.
| Structure | Number of H-bonds to the carbonyl oxygen | Wavenumber (cm–1) |
|---|---|---|
| 1 urea + 5 H2O | 2 | 1466 |
| 1 urea + 2 H2O | 2 | 1455 |
| 1 urea + 1 H2O | 1 | 1420 |
| 1 urea | 0 | 1386 |
| 2 ureas | 1 | 1408, 1421 |
| 3 ureas | 2 | 1432 |
| 4 ureas | 3 | 1441 |
| 5 ureas | 3 | 1445 |