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21 Cards in this Set
- Front
- Back
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The 5 mass spectrometer steps are...
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Vaporisation
Ionisation Acceleration Deflection Detection |
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What happens after deflection?
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Detector detects ions and produces display.
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The whole point of a spectrometer?
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To identify different isotopes in an element to find RAM of element/RMM of compound.
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To analyse an organic compound:
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R-H Bombarded with e¬s
One of the products = R-H+ (which is R-H minnus 1 e¬) |
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Which is the molecular ion peak?
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The peak for R-H+
It has the highest m/z value. |
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Why are other peaks produced?
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Due to fragmentation of organic molecule.
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Which type of molecules are detected?
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ONLY cations!
*Cations = positive ones. Anions and free radicals NOT detected. |
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Imagine the chain of events in mass spectrometer....
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e¬ hits compound.
compound is ionised. as electron is lost, a cation is formed. cation fragments to produce cation fragment & undetectable radical fragment. |
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What is the most abundant peak called?
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base peak
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imagine a m/z, cation, fragment lost table....
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The first cation has a positive charge but no fragments lost as it is an electron which is lost first.
The second cation has a corresponding lost fragments if CH3-; the next one CH3CH2- and so on. |
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A peak of 26 can have a mass charge ratio of...
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mass56:charge2+
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Mass spec of ethanol (CH3CH2OH)
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forms CH3CH2OH+ (molecular ion peak: Mr=46) on m/z line.
This can then fragment. |
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What is an M+1 peak?
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Peak due to fragments containgin a carbon-13 atom.
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What does a peak of value one less than molecular ion peak correspond to?
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The molecule losing a H.
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What does a loss of 15 correspond to?
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CH3
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If the value is 15 units less than the original or another fragment, what does this mean?
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A CH3 has been lost.
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What does a difference of 29 correspond to?
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CH3CH2
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Why is it impossible to identify all peaks?
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Complicated rearrangements of cation structures can occur.
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What are the characteristic peaks for Propanal.
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As propanal =
CH3CH2CHO, the molecular ion makes CH3CH2CHO+ a loss of H creates: CH3CHCO+ a loss of CH3CH2 makes: CHO+ |
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Characteristic peaks for Propanone?
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base peak = CH3CO+ cation
peak @ 15 = CH3+ |
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Main differences between Mass Spectra of Propanal and Propanone?
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ANAL: CHO+ cation (=loss of CH3CH2)..@ 29.
ANONE: base peak @ 15 for CH3+. peak at 43 for CH3CO+ cation. |
