Question

naturally as mixtures of two abundant isotopes. Chlorine occurs as 35Cl (75.8%) and 37Cl (24.2%); Bromine occurs as 79Br (50.7%) and 81Br (49.3%); Boron compounds also stand out owing to the two isotopes 10B (19.9%) and 11B (80.1%). For the compound Bromobenzene, C6H5Br: At what masses do the molecular ions occur

Answer 1

Answer:

Masses of bromobenzene molecular ions will occur at 156 and 158 m/z.

Explanation:

The molecular ion peak is the signal in the mass spectrum of a compound that represents the molecular ion (denoted as M). Compounds that are composed of atoms having abundant isotope also shows M +1 and M+2 peaks (depending on the isotope).

In the given bromobenzene compound, an atom of bromine is present. The two isotopes with considerable relative abundance of Br are 79Br and 81Br with a difference of two units in their mass. This means that two molecular ion peaks with a difference of two units will appear in the mass spectrum. The mass of the whole compound is 156 amu. Hence, the molecular ion peaks will appear at 156 m/z and 158 m/z due to the two isotopes of bromine.