Many molecules absorb infrared radiation
- the wavelengths they absorb depends on the natural frequencies of the stretching and bending vibrations of the individual bonds present
- INSERT DIAGRAM HERE
- by shining IR through a sample of a compound, we can determine which wavelengths are absorbed and therefore which bonds and functional groups are present
- only bonds that can change their polarity as they vibrate will interact with IR
- eg. single-bond vibrations: C-H, O-H, N-H = 4000 to 2500cm-1
- eg. triple-bond vibrations: C---C, C---N = 2500 to 1900cm-1
- eg. double-bond vibrations: C=C, C=O = 1900 to 1500cm-1
- carboxylic acids and alcohols have quite broad absorptions due to the added complication of hydrogen bonding
No comments:
Post a Comment