Table 4.
Experimental (Exp.) and B3LYP/6-311++G(d,p) calculated (Calc.; cis-I conformer) infrared spectra of monomeric 2-chlorobenzoic acid, and band assignments a.
| Exp. | Exp. [17] | Calculated | Approximate Description b |
Sym- metry |
|
|---|---|---|---|---|---|
| Gas Phase | Ar Matrix, 9 K | B3LYP | |||
| ν | ν | ν | I IR | ||
| 3576 | 3574/3565 | 3689 | 103.6 | ν(O–H) | A |
| n.obs. | n.i. | 3147 | 1.7 | ν(CH) 00++ | A |
| 3144 | n.i. | 3134 | 2.3 | ν(CH) ++00 | A |
| 3082 | n.i. | 3121 | 8.5 | ν(CH) +– –+ | A |
| 3036 (?) | n.i. | 3106 | 2.4 | ν(CH) 0+-0 | A |
| 1767 | 1766 | 1760 | 353.6 | ν(C=O) | A |
| 1595 | 1597 | 1595 | 33.3 | ν(CC) +–++–+ | A |
| 1571 | n.obs. | 1569 | 14.4 | ν(CC) +0–+0– | A |
| 1477 | 1481 | 1467 | 31.0 | ν(CC) +0– –0+, δ(CH) ++– – | A |
| 1438 | 1438 | 1431 | 25.4 | ν(CC) 0+00–0, δ(CH) +++0 | A |
| 1334/(1371) c | 1341 | 1325 | 85.0 | ν(C–O), δ(COH) | A |
| n.obs. | n.obs. | 1292 | 0.2 | ν(CC) +–+–+– | A |
| 1274 | n.obs. | 1261 | 8.8 | δ(CH) +00+ | A |
| 1185 | 1179/1176 | 1171 | 156.9 | δ(COH), ν(C-C), δ(CH) 00+0 | A |
| ~1167 | 1162 | 1162 | 39.8 | δ(CH) +–+– | A |
| 1134 | 1143 | 1134 | 48.5 | δ(CH) 0++– | A |
| 1103 | 1103/1101/1098 | 1083 | 85.6 | ν(CCl), ν(C–O) | A |
| n.obs. | n.obs. | 1041 | 14.4 | δ(ring)1 | A |
| 1045 | 1048 | 1029 | 130.8 | δ(ring)2 | A |
| n.obs. | n.obs. | 984 | 0.2 | γ(CH) +–+– | A |
| 952 | n.obs. | 958 | 2.1 | γ(CH) +– –+ | A |
| 864 | n.obs. | 867 | 0.6 | γ(CH) ++– – | A |
| 800 | n.obs. | 792 | 2.2 | γ(C=O) | A |
| 782/775 d | n.obs. | 775 | 13.2 | ν(C–C), δ(ring)3, δ(OCO) | A |
| 746 | 749/747 | 743 | 89.6 | γ(CH) ++++ | A |
| 707 | 686 | 690 | 21.8 | τ(ring)1 | A |
| 690 | n.obs. | 677 | 30.4 | ν(CCl), δ(OCO), δ(ring)3 | A |
| 630 | 631 | 627 | 43.7 | δ(OCO) | A |
| 576 | n.obs. | 575 | 78.3 | τ(C–O) | A |
| n.i. | n.obs. | 526 | 12.2 | γ(C-[CCC]) | A |
| n.i. | n.i. | 483 | 2.3 | τ(ring)2 | A |
| n.i. | n.i. | 440 | 3.9 | δ(ring)3 | A |
| n.i. | n.i. | 416 | 6.9 | τ(ring)3 | A |
| n.i. | n.i. | 350 | 1.7 | δ(ring)4 | A |
| n.i. | n.i. | 293 | 0.6 | δ(CCl) | A |
| n.i. | n.i. | 205 | 1.8 | γ(CCl) | A |
| n.i. | n.i. | 192 | 0.7 | γ(COOH) | A |
| n.i. | n.i. | 114 | 0.2 | w(COOH) | A |
| n.i. | n.i. | 28 | 0.8 | τ(C–C) | A |
a Wavenumbers (ν) in cm−1, calculated infrared intensities (IIR) in km·mol−1; n.obs., not observed; n.i., not investigated; ?, uncertain. b Approximate description was obtained using the vibrations animation module of Chemcraft [63]; ν, stretching; δ, bending; w, wagging; γ, rocking; τ, torsion; the symbols +, – and 0 placed in front of the ν(CC), ν(CH), δ(CH) and γ(CH) ring coordinates indicate the movement (distending, compressing, staying, respectively) of the related bonds, starting from that located ortho to the C=O bond of the carboxylic group and proceeding anti-clockwise through the ring. c Band due to conformer cis-II. d Fermi interaction with τ(C-O) + γ(CCl).