- Infrared Spectroscopy
- Infrared radiation makes some bonds vibrate more than others.
- In infrared (IR) spectroscopy, IR radiation is passed through a sample. The radiation is absorbed by covalent bonds, increasing their vibrational energy.
- Bonds between different atoms absorb different frequencies of IR radiation, e.g. a C-H bond will absorb a different amount of energy than an O-H bond.
- Bonds in different molecules absorb different frequencies of radiation, e.g. an O-H bond in an alcohol will absorb a different amount of energy to an O-H bond in a carboxylic acid.
- An infrared spectrum can show if a reaction has happened. Some functional groups may disappear and others may appear, showing that the molecule has changed.
- Example: if an alcohol is oxidised to an aldehyde, the O-H absorption will disappear and the C=O absorption will appear.