Table 7.
Experimental (Exp.) and B3LYP/6-311++G(d,p) calculated (Calc.) infrared spectra of monomeric 2,6-dichlorobenzoic acid, and band assignments a.
| Exp. | Calculated | Approximate | Sym- | |
|---|---|---|---|---|
| Gas Phase | B3LYP | Description b | metry | |
| ν | ν | I IR | ||
| 3564 | 3660 | 86.1 | ν(O–H) | A′ |
| 3130 | 3141 | 1.0 | ν(CH) +++ | A′ |
| n.obs. | 3137 | 0.1 | ν(CH) +0– | A″ |
| 3073 | 3114 | 3.7 | ν(CH) +–+ | A′ |
| 1780 | 1779 | 330.5 | ν(C=O) | A′ |
| 1587 | 1587 | 33.6 | ν(CC) +–++–+ | A′ |
| 1567 | 1563 | 49.7 | ν(CC) +0–+0– | A″ |
| 1455 (?) | 1436 | 5.2 | ν(CC) +0– –0+, δ(CH) +0– | A′ |
| 1434 | 1429 | 79.6 | ν(CC) 0+00–0, δ(CH) +++ | A″ |
| 1349/1297 c | 1322 | 70.9 | ν(C–O), δ(COH) | A′ |
| 1266 | 1277 | 2.4 | ν(CC) +–+–+– | A″ |
| 1192 | 1193 | 25.0 | δ(CH) +0+ | A″ |
| 1192 | 1189 | 130.9 | δ(COH), δ(ring) 1 | A′ |
| 1159 | 1153 | 7.3 | δ(CH) 0+0 | A″ |
| 1127 | 1120 | 172.4 | ν(C–O), δ(COH), ν(CCl2) sym, δ(CH) +0– | A′ |
| 1090/1083 d | 1073 | 9.1 | ν(CCl2) sym | A′ |
| 1047 | 1043 | 24.0 | δ(ring)2 | A′ |
| n.obs. | 967 | 1.0 | γ(CH) +–+ | A′ |
| n.obs. | 886 | 0.002 | γ(CH) +0– | A″ |
| 804 | 785 | 37.6 | ν(CCl2) asym, γ(C=O) | A″ |
| 786 | 768 | 26.5 | ν(C-C), γ(CH) +++ | A′ |
| 777 | 766 | 25.5 | γ(CH) +++ | A′ |
| 747/740 e | 746 | 89.6 | γ(C=O), ν(CCl2) asym | A″ |
| 727 | 729 | 15.4 | τ(ring)1 | A′ |
| 650 | 641 | 35.8 | δ(OCO) | A′ |
| 582 | 597 | 71.7 | τ(C-O) | A″ |
| n.obs. | 567 | 0.3 | τ(ring)2 | A |
| n.i. | 518 | 0.3 | τ(ring)3 | A″ |
| n.i. | 454 | 18.2 | ν(C–C), ν(CCl2) sym | A′ |
| n.i. | 432 | 1.6 | δ(ring)3 | A″ |
| n.i. | 382 | 0.3 | γ(CCl2) sym | A′ |
| n.i. | 376 | 2.9 | δ(CCl2) asym | A″ |
| n.i. | 313 | 0.5 | δ(ring)4 | A′ |
| n.i. | 195 | 0.001 | γ(CCl2) asym | A″ |
| n.i. | 185 | 0.01 | δ(CCl2) sym | A′ |
| n.i. | 164 | 2.9 | γ(C-[CCC]) | A′ |
| n.i. | 135 | 0.2 | w(COOH) | A″ |
| n.i. | 74 | 0.8 | γ(COOH) | A′ |
| n.i. | 38 | 2.1 | 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 Fermi interaction with 2 × δ(OCO). d Fermi interaction with τ(ring)2 + τ(ring)3. e Fermi interaction with 2 × δ(CCl2) asym.