IR11. Appendix: IR Table of Organic Compounds
- Page ID
- 4168
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Table of IR Absorptions Common. Note: strong, medium, weak refers to the length of the peak (in the y axis direction). Note: spectra taken by ATR method (used at CSB/SJU) have weaker peaks between 4000-2500 cm-1 compared to reference spectra taken by transmittance methods (typical on SDBS and other sites).
| Approximate Frequency (cm-1) | Description | Bond Vibration | Notes |
| 3500 - 3200 | broad, round | O-H | much broader, lower frequency (3200-2500) if next to C=O |
| 3400-3300 | weak, triangular | N-H | stronger if next to C=O |
| 3300 | medium-strong | =C-H (sp C-H) | |
| 3100-3000 | weak-medium | =C-H (sp2 C-H) | can get bigger if lots of bonds present |
| 3000-2900 | weak-medium | -C-H (sp3 C-H) | can get bigger if lots of bonds present |
| 2800 and 2700 | medium | C-H in O=C-H | two peaks; "alligator jaws" |
| 2250 | medium | C=N | |
| 2250-2100 | weak-medium | C=C | stronger if near electronegative atoms |
| 1800-1600 | strong | C=O | lower frequency (1650-1550) if attached to O or N middle frequency if attached to C, H higher frequency (1800) if attached to Cl |
| 1650-1450 | weak-medium | C=C | lower frequency (1600-1450) if conjugated (i.e. C=C-C=C) often several if benzene present |
| 1450 | weak-medium | H-C-H bend | |
| 1300 - 1000 | medium-strong | C-O | higher frequency (1200-1300) if conjugated (i.e. O=C-O or C=C-O) |
| 1250-1000 | medium | C-N | |
| 1000-650 | strong | C=C-H bend | often several if benzene present |
Contributors and Attributions
Chris P Schaller, Ph.D., (College of Saint Benedict / Saint John's University)