BRAINCAKEMass Spectrometry
Revision notes for Mass Spectrometry in Edexcel Chemistry (8CH0). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- Mass SpectrometryMass spectrometry can be used to determine the relative isotopic masses of isotopes of elements or the relative molecular masses of molecules.
- The Molecular Ion PeakFor the mass spectrum of a molecule, the main peak with the largest m/z value (ignoring the small M+1 peak caused by carbon-13).
- Other PeaksIn organic molecules, a very small peak to the right of the molecular ion peak indicates the presence of the C-13 isotope.
- FragmentationPeaks with m/z values smaller than the molecular ion peak are a result of fragmentation.
- Mass Spectrum Example 1Example 1: ethanol, CH3CH2OH (Mr = 46) To interpret a mass spectrum, first find the molecular ion peak, then work out what each fragment peak has…
- Mass Spectrum Example 2Example 2: propanal and propanone Propanal, CH3CH2CHO, and propanone, CH3COCH3, are structural isomers with the formula C3H6O.
- Mass Spectrum Example 3Example 3: pentan-2-one and pentan-3-one Pentan-2-one, CH3COCH2CH2CH3, and pentan-3-one, CH3CH2COCH2CH3, are position isomers with the formula C5H10O.
- Mass Spectrum Example 4Example 4: chloroethane, CH3CH2Cl Chlorine has two isotopes, chlorine-35 and chlorine-37, which occur in the ratio of about 3:1.
- Mass Spectrum Example 5Example 5: identifying an unknown halogenoalkane A compound gives two molecular ion peaks of equal height at m/z 108 and 110, and a large peak at…