Answer
IR Spectrum Interpretation and Structure Suggestion
Key IR Absorption Peaks
| Wavenumber (cm⁻¹) | Intensity | Functional Group / Vibration |
|---|---|---|
| 3344, 3223 | Strong, Broad | N–H Stretch (Amide or Amine) |
| 2985 | Medium | C–H Stretch (Alkane) |
| 1685 | Strong | C=O Stretch (Carbonyl / Amide) |
| 1281 | Medium | C–N or C–O Stretch |
| 1173, 773, 504 | Various | Fingerprint region, supports C–N / C–O bonding |
Functional Group Analysis
- Broad N–H peaks indicate the presence of an amide group.
- The strong carbonyl stretch confirms a C=O group typical of amides.
- C–H stretches suggest aliphatic chains are present.
- C–N/C–O regions support amide functionality.
Molecular Formula and Unsaturation
Molecular Formula: C9H11NO2
Degree of Unsaturation (DU):
DU = (2×9 + 2 + 1 – 11)/2 = 5
➤ Indicates one amide group and one aromatic ring (benzene)
Proposed Structure: Phenylacetamide
The compound contains:
- An aromatic ring (benzene) → 4 DU
- An amide group (–CONH2) → 1 DU
- A CH2 bridge connecting the ring to the amide
Molecular Breakdown:
- Carbon (C): 9 (6 from ring, 1 CH2, 1 C=O, 1 amide)
- Hydrogen (H): 11 (ring + CH2 + NH2)
- Nitrogen (N): 1
- Oxygen (O): 2