MASS SPECTROMETRY (MS)

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MASSSPECTROMETRY(MS)
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Mass Spectrometry
MS gives an exact measure of molecular mass. An
electron beam (70ev) dislodges an electron from a
sample giving M , a radical cation. A potential
difference of 10000 v accelerates the ions.
Radicals are not affected. The ions pass through
a magnetic field causing the ions to curve
(heavier ones less than lighter ones). Radicals
are not affected by the magnetic field. Ions
collide with the detector to give a spectrum with
particles arranged by mass.

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Mass Spectrometry
The most intense peak is called the base peak.
The highest MW peak is the usually the molecular
ion, M or M, and equals the MW of the compound.
Isotopes of certain atoms produce M1 and M2
peaks, some of which are very characteristic. Odd
numbers of nitrogen give an odd M peak. The
radical cation is unstable and fragments during
flight. Fragment weights can assist in
determining structure. M ? A B or
A B



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Isotopic Abundances
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Mass Spectrometry Linear Alkane
CH3CH2CH2CH2CH2CH3
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Mass Spectrometry Branched Alkane
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Mass Spectrometry Branched Alkane
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Mass Spectrometry - Alkene
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Mass Spectrometry - Chloroalkane
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Mass Spectrometry - Bromoalkane
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Mass Spectrometry Sulfide
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Mass Spectrometry - Alcohol
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ENDMASSSPECTROMETRY(MS)