Mass spectrometry in organic compounds Flashcards
the molecular ion peak is
the peak which indicates the species formed form the molecule by the loss of one electron
on a mass spectrum, the molecular ion peak is the
last peak on the graph, with the greatest m/z ratio
each peak on a mass spectrum for a single element represents ……….of the element
an isotope
m/z stands for
mass to charge ratio
the positive ion used in mass spectrometry is produced by
firing a stream of high energy electrons to the test species so that the electrons knock off an electron in the outer shell of the test species.
the m/z value of the molecular ion peak shows the
relative molecular mass of a compound, or relative atomic mass of an element
sometimes a very small peak appears on the right of the molecular ion peak. this is the
M+1 peak
the M+1 peak is caused because
of the presence of a naturally occurring carbon-13 isotope
approximately ….% of all carbon atoms are 12-C while most of the remaining …..% is 13-C
99% is 12-C while most of the 1% is 13-C
the other peaks that appear with lower values in the mass spectrum of compounds are due to : (3 items)
-fragmentation in the mass spectrometer
-rearrangement reactions
loss of more than one electron
fragmentation occurs when
the molecular ion breaks into smaller pieces
when a C-C bond in the molecular ion is broken, the two species formed are:
a positive ion
a neutral species, usually a radical
the fragmentation of an ethane ion will produce:
CH3+
CH3
a typical way of labelling the vertical axis of a mass spectrum is
relative intensity (%), always from 0%- 100%
a typical way of labelling the horizontal axis of a mass spectrum is
m/z (no units)
