Table 1. Dihedral angles in the acid-base unit (°), hydrogen position and ΔpK a .
A, B, C, D and E are the dihedral angles between the C1–C6 ring and the N2/C8–C16 ring system, between the O1/C7/O2 plane and the N2/C8–C16 ring system, between the C1–C6 ring and the O1/C7/O2 plane, between the C1–C6 ring and the O3/N1/O4 plane, and between the N2/C8–C16 ring system and the nitro group attached to it, respectively.
| A | B | C | D | E | H-atom site | ΔpK a | |
|---|---|---|---|---|---|---|---|
| 2-Chloro-4-nitrobenzoic acid | |||||||
| (I) | 69.15 (5) | 26.60 (16) | 51.29 (17) | 17.77 (14) | N | 3.62 | |
| a | 3.15 (7) | 43.0 (2) | 39.9 (2) | 12.2 (2) | O | 2.86 | |
| b | 1.11 (4) | 28.59 (12) | 29.36 (12) | 8.24 (11) | O/N | 3.16 | |
| c | 3.94 (17) | 7.5 (5) | 4.3 (5) | 2.5 (5) | 36.2 (5) | O | 0.76 |
| 2-Chloro-5-nitrobenzoic acid | |||||||
| (II) | 13.81 (10) | 14.1 (3) | 24.6 (3) | 9.7 (3) | O | 3.44 | |
| a | 1.92 (4) | 22.48 (14) | 21.02 (14) | 0.50 (13) | O | 2.68 | |
| b | 2.15 (4) | 24.51 (15) | 22.63 (15) | 0.77 (14) | O | 2.98 | |
| 2-Chloro-6-nitrobenzoic acid | |||||||
| (III) | 61.05 (5) | 35.42 (16) | 84.53 (16) | 21.7 (8), 14.7 (14) | O/N | 4.04 | |
| 3-Chloro-2-nitrobenzoic acid | |||||||
| (IV) | 59.45 (4) | 37.30 (13) | 22.39 (13) | 75.20 (13) | O/N | 3.84 | |
| a | 4.71 (5) | 6.18 (16) | 9.22 (16) | 84.97 (13) | O/N | 3.08 | |
| b | 14.50 (5) | 12.55 (18) | 3.14 (18) | 85.04 (11) | O/N | 3.38 | |
| c | 2.59 (4) | 9.95 (12) | 9.45 (12) | 86.14 (13) | 31.67 (11) | O | 0.98 |
| d | 10.99 (4) | 12.08 (13) | 2.40 (13) | 88.54 (13) | 5.58 (12) | O | 1.42 |
| 4-Chloro-2-nitrobenzoic acid | |||||||
| (V) | 61.21 (5) | 67.42 (14) | 10.22 (14) | 80.76 (15) | N | 3.69 | |
| a | 31.65 (4) | 18.77 (13) | 13.71 (13) | 76.44 (17) | O/N | 2.93 | |
| b | 30.39 (9) | 21.7 (3) | 16.4 (3) | 74.4 (3) | O/N | 3.23 | |
| 5-Chloro-2-nitrobenzoic acid | |||||||
| (VI) | 58.90 (4) | 23.54 (13) | 35.43 (13) | 57.13 (11) | N | 3.80 | |
| a | 54.43 (5) | 5.41 (15) | 49.95 (15) | 33.31 (13) | O/N | 3.04 | |
| c | 37.37 (6) | 2.9 (2) | 40.3 (2) | 47.12 (19) | 11.3 (2) | O | 0.94 |