TA : Sarah Wondmeneh
30 January, 2013
Experiment 3 - PreLab
When bromine is present in a compound, the M + 2 ion becomes very significant. This is
because bromine is comprised of two isotopes ( Br and Br) in a nearly 1:1 ratio in
naturally occurring substances. If a compound contains bromine, the M+ and M + 2 ions
are present at almost equal intensities. As a result, the relative intensities of the
molecular ion peak and its associated isotope peaks directly indicate the number of
bromine atoms in the molecular formula.
The peaks would be observed at 79Br (79m/z), 8Br (81m/z), 79Br- Br (158m/z), 79Br-
81 81 81
Br (160m/z) and Br- Br (162m/z) respectively.
The relative heights of the peaks would be the following:
Highest peak when Br is composed of 7Br- Br and the lowest peak would be when it
consists of Br