BRAINCAKEInfrared Spectroscopy
Infrared (IR) spectroscopy is an analytical technique that shows which bonds, and so which functional groups, are present in a molecule.
A beam of infrared radiation covering a range of frequencies is passed through a sample. Covalent bonds absorb IR radiation at particular frequencies. The instrument measures how much radiation passes through the sample at each frequency.
The result is an IR spectrum:
The x-axis is wavenumber in cm−1, usually running from 4000 on the left down to about 500 on the right. Wavenumber is proportional to frequency.
The y-axis is transmittance in %. 100% means no radiation is absorbed.
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More in Organic Analysis
- Identifying Functional Groups
- Test Tube Tests for Organic Compounds
- High Resolution Mass Spectrometry
- Precise Relative Molecular Mass
- Bond Vibrations and IR Absorption
- The Fingerprint Region
- Interpreting IR Spectra
- Infrared Radiation and the Greenhouse Effect
All 9 lessons in Organic Analysis · All AQA AS-level Chemistry topics