Chlorine and Bromine-Containing Compounds in a Mass Spectrum

Identifying Chlorine and Bromine-Containing Compounds in a Mass Spectrum 

Mass spectrometry is particularly valuable in identifying chlorine and bromine by their isotopic abundances. The atomic mass of chlorine is 35.5. Chlorine has two isotopes, C1 and C1. The atomic mass corresponds to an isotopic ratio 5Q/37q 3.1 p j- example, the mass spectrum of 

2-Chloropropane ioni2es to give two parent ions that differ by two mass units. The ratio of the peak intensities is 3 1, showing that one parent ion contains Cl and the other one contains Cl. Fragmentation of either parent peak by loss of Cl or Cl gives the base peak of mass 43. It is an isopropyl cation, 

The parent ion can lose a chlorine atom to give an isopropyl carbocation in a process called a-cleav-age. The resulting ion has an mlz of 43. This process produces the base peak. 

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