🟣 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!
Study this topic on the go
Get flashcards and quizzes in ChemEasy, or plan your revision with ChemPlan IB.