AS Chemistry A OCR - Organic Analytical Techniques - Revision Cards in A Level and IB Chemistry

Infared Spectroscopy

Infared Radiation causes bonds to vibrate/stretch more and absorb energy.
Atmospheric Gases (CO2, H2O, CH4)
- Contain C=O, O-H and C-H bonds.
- Energy absorbtion by these bonds is believed to be the reason for global warming.
- The reason we use less energy now is because power plants create these atmospheric gases.
Infared Spectra
- Alcohol
  - Peak for the OH bond around 3600
- Ketone/Aldehyde
  - Peak for C=O around 1700
- Carboxylic Acid
  - Peak for the broad carboxylic acid OH bond around 3600
  - Peak for the C=O around 1700.
IR Spectroscopy is also used for breathalysers
- Measured the amount of ethanol in the breath
  - Look for the OH bond and the CH bond groups.

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Molecular Ion Peak (M+) is the peak furthest to the right.
- Possible M+1 peak due to carbon-13.
Limited to Ions with single charges.
When fragmentation occurs, they do not reform or recombine.
- This means that if you have a C2H5+ fragment, somewhere in the structure there is a section that has the formula C2H5.

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