Molecules absorb infrared radiation by vibrating. The amount of vibration depends on
- bond strength
- bond length
- mass of atoms within bond
Infrared spectrum shows functional groups of substances. Each peak represents the absorbsance of infrared radiation energy of a particular bond in the molecule.
Look out for:
- Aldehydes have C=O bonds (1640=1750) made through DISTILLATION of primary alcohols
- Ketones also have C=O bonds and are made by REFLUX of secondary alcohols
- Esters have C=O bonds, C-O bonds (1000 to 1300).
- Carboxylic acids have the C=O and C-O and O-H bonds and are made from oxidation of aldehydes.
- MOST have peak at 3000 showing a C-H bond (not broad so…