✅7 - Modern Analytical Techniques I
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What is mass spectrometry used for?
Identifying compounds
What is the molecular ion, M+?
The molecule with an electron removed
What is the molecular ion peak?
The peak with the highest m/z value
What does the Molecule ion peak show?
The relative formula mass of the compound
What can the molecular ion be broken into?
Smaller fragments
What is a fragmentation pattern?
The mass spectrum shown by all the fragments
How can fragments be identified?
By their molecular mass
What is mass spectrometry used to differentiate between?
Similar molecules
How is Infrared spectroscopy carried out?
A beam of IR radiation is passed through a sample of a chemical
How does the IR radiation affect bonds?
It is absorbed by covalent bonds in the molecules, increasing their vibrational energy
How can IR spectroscopy be used to differentiate between bonds?
Bonds between differnet atoms absorb different frequencies of IR radiation
How does the location of a bond affect its absorption?
In the frequency absorbed, so OH groups on alcohols and carboxylic acids have different frequencies of absorption
What does in infrared spectrometer produce?
A graph
What is plotted on the y axis of an IR graph?
Transmittance
What is plotted on the x axis of an IR graph
Wavenumber - 1/wavelength in cm
How can IR spectroscopy show if a reaction has happened?
If the functional group has changed on the graph
How would an IR spectroscopy graph change if an alcohol was oxidised to an aldehyde?
The O-H absorption would disappear and and C=O would appear
How would an IR spectroscopy graph change is an aldehyde was oxidised to a carboxylic acid?
The O-H peak would appear at a slightly lower frequency and the C=O peak will remain
What does IR radiation cause covalent bonds to do?
Vibrate
What do the peaks on the IR graph show you?
Where the radiation is being absorbed