Table 4.
Coordination numbers (CN) and number of hydrogen bonds (nHB) in aqueous solution a.
| Structures in Schemes | O/Ow | O/Hw | Nt/Ow | Nt/Hw | Nc/Ow | Nc/Hw | (N)Ht/Ow | (N)Hc/Ow | nHB b |
|---|---|---|---|---|---|---|---|---|---|
| CH2=CH–CH–NH (1) | 3.4 | 2.0 | 0.9 | 2.3 (−3.0) c | |||||
| CH2=CH–CH–NH (2) | 3.1 | 2.1 | 0.8 | 2.4 (−3.0) c | |||||
| O=CH–CH=NH (5) | 1.4 | 1.3 | 2.5 | 1.3 | 1.0 | 2.9 (−3.0) | |||
| O=CH–CH=NH (7) | - d | 1.1 | 2.0 | 1.0 | 0.8 | 1.4 (−3.5) c | |||
| O=CH–CH=NH (8) | 1.9 | 1.5 | 2.8 | 1.3 | 1.0 | 3.0 (−3.5) | |||
| O=C=CH–NH2 (9) | - d | 0.6 e | - d | 1.0 | 0.7 | 2.3 (−2.5) c | |||
| HN=CH–CH=NH (10) | 2.8 | 1.5 | 0.8 | 3.9 (−3.0) | |||||
| HN=CH–CH=NH (11) | 2.9, 3.1 | 1.3, 1.7 | 1.0, 1.0 | 4.4 (−3.0) | |||||
| HN=CH–CH=NH (12) | 3.0 | 1.5 | 0.95 | 4.1 (−3.0) | |||||
| HN=CH–CH=NH (13) f | 2.1, 2.7 | 1.3, 1.0 | 0.4, 0.95 | 2.6 (−3.0) | |||||
| TS (from 10 toward 15)f | 3.2 | 1.6 | 1.0 | 4.3 (−3.0) | |||||
| HN=CH–CH=NH (15) g | 2.9 | 1.6 | 1.0 | 4.7 (−2.5) |
a For species 9, the nitrogen/X CN values appear with subscript “t”, for 11 and 13 coordination numbers refer to nitrogens from the left to right in Scheme 2. Integration limits: 305 pm (O/Ow), 240–255 pm (O/Hw), 325–355 pm (N/Ow), 245–260 pm (N/Hw), 235–255 pm (H/Ow); b Integration limit of the pedf in parentheses; c No resolved first peak below 350 pm; d Middle of a plateau; e End of a plateau at 225 pm; f First and second CN values for the right-hand and the left-hand side N–H atoms, respectively; and g Equivalent nitrogens in gauche position.