Table 3. Short hydrogen bonds with N—H donors from the Cambridge Structural Database.
Mean distances and angles are given along with the sample standard deviation†. D, donor; A, acceptor.
| Donor group | Acceptor group | No. of fragments | d(D⋯A) (Å) | ∠(D—H⋯A) (°) |
|---|---|---|---|---|
| Imidazole | Carboxylate | 53 | 2.75 (12) | 164 (12) |
| Imidazole | Aliphatic OH | 10 | 2.81 (5) | 166 (10) |
| Aliphatic NH+ | Carboxylate | 306 | 2.82 (8) | 161 (12) |
| Imidazole | Carboxylic acid | 9 | 2.83 (9) | 155 (23) |
| Indole | Carboxylate | 8 | 2.84 (7) | 161 (10) |
| Imidazole | Amide O | 5 | 2.85 (13) | 162 (4) |
| Aliphatic NH+ | Amide O | 16 | 2.85 (7) | 151 (18) |
| Aliphatic NH+ | Aliphatic OH | 24 | 2.85 (9) | 157 (14) |
| Indole | Aliphatic OH | 15 | 2.87 (5) | 159 (13) |
| Imidazole | Imidazole | 63 | 2.88 (7) | 167 (8) |
| Backbone NH | Carboxylate | 43 | 2.89 (6) | 160 (11) |
| Indole | Amide O | 11 | 2.89 (6) | 162 (11) |
| Aliphatic NH+ | Carboxylic acid | 52 | 2.89 (8) | 149 (15) |
| Aliphatic NH+ | Phenol | 15 | 2.89 (7) | 153 (13) |
| Guanidinium | Carboxylate | 59 | 2.90 (7) | 163 (12) |
| Backbone NH | Amide O | 415 | 2.91 (7) | 162 (11) |
| Backbone NH | Aliphatic OH | 22 | 2.93 (5) | 164 (13) |
| Guanidinium | Aliphatic OH | 5 | 2.93 (5) | 161 (7) |
| Amide NH side chain | Amide O | 65 | 2.93 (6) | 165 (10) |
| Indole | Carboxylic acid | 22 | 2.93 (8) | 159 (11) |
| Guanidinium | Carboxylic acid | 12 | 2.93 (7) | 161 (13) |
| Backbone NH | Carboxylic acid | 61 | 2.95 (6) | 161 (10) |
| Amide NH side chain | Carboxylate | 15 | 2.95 (5) | 159 (15) |
| Guanidinium | Phenol | 5 | 2.96 (6) | 150 (10) |
| Backbone NH | Phenol | 7 | 2.97 (7) | 160 (13) |
| Amide NH side chain | Aliphatic OH | 23 | 2.97 (7) | 160 (13) |
| Amide NH side chain | Carboxylic acid | 5 | 2.98 (4) | 165 (6) |
†
Sample standard deviation = 
.