In depth and simple to understand class notes taken over the course of 2 years in a highly accredited IB school for Chemistry HL, in regards to the topic of Mass spectrometry
This includes diagrams, annotations, extensive notes and explanations and they are the notes that have solely led me to an...
- The IHD provides clue to what the structure once the formula is known
- Measure of how many molecules of H2 would be needed in theory to
- convert the molecule to the corresponding saturated, non-cyclic molecule.
- If the compound is already saturated, then the Index is 0
- The number from the formula shows how many H2 are needed to add to the compound
to make it saturated (no double bonds)
- Formula does not work for cyclic compounds, will say it is unsaturated even though it is
- Formula tells us that you need one more H2 to make the compound non-cyclic
Table 28 of the data book has info
Using mass spec to find the type of element
- The abundance of the isotope x the number of the isotope
- 85.3%(10) + 14.7%(11)/100 = molar mass
- When putting an organic compound through spectrometer, the process is very vigorous and the
compound will fragment
- In the mass spec, we can see all the different possibilities of fragmentation
- Spectra obtained for organic molecules have many peaks. Each peak is due to a particular
fragment with a certain m/z value.
- Highest m/z value usually corresponds to the molecular ion
- Its position provides information about the molecular mass of a substance
- The tallest peaks come from the most stable species
Interpretation of thousands of spectra has shown that many classes of
organic compound show characteristic fragmentation patterns due to
their functional groups.
It is possible to identify the type of compound from its spectrum by
looking at the…
, Infrared spectroscopy
Atoms vibrate by different methods, in different ways
- Covalent bonds vibrate
- Affected by: Bond strength, molar mass, polarity
- When shining infrared light on the molecule, the frequency of the vibrations double
- V1 is when the atom is vibrating normally, V2 is when the vibrations double due to
infrared light
- Table 26: Shows what bonds absorb what wavelengths
- Frequency (wavenumber) = 1/lambda
- If lambda (wavelength) is longer, it has lower frequency and lower energy
- If lambda is shorter, has higher frequency and higher energy
- High polarity, strong bond and light atom means quicker vibrations, means high
frequency, higher energy, shorter wavelength and will absorb higher energy of
Infrared light, higher wavenumber
The type of infrared light that a
compound absorbs can be seen
when shining the light through the
compound onto a sheet of paper
behind, making a graph.
Strong absorption means the line
on the graph will drop greatly,
medium is a medium drop.
Broad means a thick drop, two
bang
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