An FTIR spectroscopy chart is a graphical representation of how molecules absorb infrared light, revealing their chemical structure. This technique measures molecular vibrations to identify substances.
FTIR (Fourier-change infrared spectroscopy) shines infrared light through a sample. Molecules absorb specific wavelengths, creating peaks on the chart. These peaks correspond to bond vibrations between atoms.
The x-axis shows wavenumbers (cm⁻¹), indicating light frequency. The y-axis shows absorbance or transmittance. Each molecule produces a unique pattern, like a fingerprint.
FTIR charts have distinct features:
For example, a peak around 1700 cm⁻¹ often indicates a carbonyl group (C=O). A broad peak near 3400 cm⁻¹ suggests hydroxyl groups (O-H).
Scientists use FTIR spectroscopy charts to:
In my lab work, I used an FTIR spectrometer to confirm the presence of esters in a reaction mixture. The chart showed clear peaks at 1740 cm⁻¹ and 1200 cm⁻¹, matching reference spectra for esters.
| Technique | Light Range | Key Use |
|---|---|---|
| FTIR | Infrared (400-4000 cm⁻¹) | Identifying functional groups |
| UV-Vis | Ultraviolet-visible (200-800 nm) | Measuring electronic transitions |
| NMR | Radiofrequency | Studying molecular environments |
Unlike UV-Vis spectroscopy, which examines electronic transitions, FTIR focuses on vibrational modes. NMR spectroscopy provides details about molecular environments but requires more complex equipment.
To read an FTIR chart:
A common mistake is assuming all peaks represent the same bond type. For instance, a peak at 1600 cm⁻¹ could indicate C=C stretching or N-H bending, requiring additional context.
FTIR has some drawbacks:
Researchers often combine FTIR with other techniques like Raman spectroscopy for complete analysis. According to the Journal of Molecular Structure, FTIR accuracy improves when paired with computational modeling.