Question

Compare position of molecular ion peaks for (bromobenzene and 4-bromotoluene) how are they different/similar? Also, compare the fragments that formed (how are they different and similar?)

Answer 1

Mass spectrum of bromobenzene with a molecular weight of 157. The molecular ions at 156 and 158 represent species that contain either the lighter or heavier isotope of bromine, respectively, demonstrating that the natural abundance of each isotope is roughly 50%. The peak at 77 represents the loss of bromine during fragmentation to leave behind the C6H5⁺ ion.

Mass spectrum of bromobenzene with a molecular weight of 171. The molecular ions at 170 and 172 represent species that contain either the lighter or heavier isotope of bromine, respectively, demonstrating that the natural abundance of each isotope is roughly 50%. The peak at 91 represents the loss of bromine during fragmentation to leave behind the C7H7⁺ ion.