🟣 This is Higher Level (HL) content.
Key Absorptions (From Data Booklet)
| Bond | Wavenumber / cm⁻¹ | Appearance | Indicates |
|---|---|---|---|
| O–H (alcohol) | 3200–3550 | Broad | Alcohol |
| O–H (acid) | 2500–3300 | Very broad | Carboxylic acid |
| N–H | 3300–3500 | Medium, often 2 peaks | Amine / amide |
| C=O | 1700–1750 | Strong, sharp | Aldehyde, ketone, acid, ester |
| C–O | 1000–1300 | Strong | Alcohol, ester, ether |
| C=C | 1620–1680 | Medium | Alkene |
🔑 Fingerprint Region
Below ~1400 cm⁻¹ is the fingerprint region. Complex, unique to each molecule. Used for matching against known spectra, not for identifying individual bonds.
⚠️ Examiner Tip
A broad O–H peak plus a sharp C=O peak = carboxylic acid. A sharp C=O without O–H = aldehyde, ketone, or ester. Always check for combinations!