Modern Analytical Techniques Flashcards
What happens to a covalent bond when it absorbs infrared radiation?
It vibrates more
What is an absorption peak?
The energy absorbed by a covalent bond is shown as an absorption peakon an infrared spectrum
What does infrared spectroscopy allow us to identify?
Particular bonds and hence the functional groups in a molecule
What gases are named the greenhouse gases?
- Water vapour
- Carbon dioxide
- Methane
What are greenhouse gases able to do in terms of wavelength radiation?
They are able to absorb longer wavelength radiation which is re-emitted from the Earth’s surface (leads to the temperature of the atmosphere to increase - global warming)
Name 2 applications of infrared spectroscopy
- Modern breathalysers measure ethanol in the breath (by identifying the O-H bond of ethanol) to provide evidence for Law Courts
- To monitor the gases causing air pollution e.g. CO and NO from car emissions
How does a organic molecule change when placed in a mass spectrometer?
The molecules is ionised and loses an electron to become a molecular ion, M+. This produces a peak furthest to the right on the mass spectrum - the M+ peak. The m/z value of the M+ peak is equal to the Mr of the molecule
What is an M+1 peak?
You may see a very small peak, one unit beyond the M+ peak, this is due to the presence of a C-13 isotope which makes up 1.11% of all carbon atoms
What technique can be used to identify the structure of the M+ ion?
Fragmentation - splitting up the molecule into pieces. This gives a certain Mr’s which if present on the mass spectrum, indicates the structure of the ion. These peaks on the spectrum are known as the fragmentation patterns
Give examples of mass spectrometry in organic chemistry
- Detecting drugs (e.g. steroids in sport)
- Analysing molecules in space (e.g. Mars space probe)
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