Mass spectra & IR -2
- Created by: Shannon
- Created on: 09-05-14 16:02
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- Mass spectra & IR
- Mass spectrometry can differentiate between similar molecules
- Mass spectrometry can tell 2 similar molecules apart, because they won't produce exactly the same set of fragments
- E.g Propanal and Propanone
- Have the same Mr but possess different structures, so different fragments are produced
- Propanal will produce a C2H5 fragment, when propanone won't
- Have the same Mr but possess different structures, so different fragments are produced
- Mass spectrometry is used to find...
- Relative isotopic masses
- The abundance of different isotopes
- Relatively molecular mass
- Look at the molecular ion peak
- The molecular ion can be broken into fragments
- Fragmentation pattern seen
- The molecular ion can be broken into fragments
- Look at the molecular ion peak
- Infrared radiation
- Some molecules can absorb the energy from IR
- Makes their covalent bonds vibrate
- Only molecules made of different atoms can absorb IR
- Polarities of the bond changes as they vibrate
- E.g CO2, H2O, NO & CH4
- Gases that absorb IR are called greenhouses gases
- Stops some of the radiation emitted by the Earth from escaping
- Trapped in atmosphere
- Stops some of the radiation emitted by the Earth from escaping
- IR spectroscopy helps to identify organic molecules
- Shows what frequencies of radiation the molecule is absorbing
- Can identify functional groups
- C-H stretch in alkanes, alkenes and aldehydes
- O-H stretch in alcohols and carboxylic acids
- N-H stretch in amines
- C=O stretch in aldehydes and ketones
- C-X stretch in halogenoalkanes
- Can identify functional groups
- Shows what frequencies of radiation the molecule is absorbing
- Some molecules can absorb the energy from IR
- Mass spectrometry can differentiate between similar molecules
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