Halogenated compounds arc particularly easy to identify by their mass spectra because both chlorine and bromine occur naturally as mixtures of two abundant isotopes. Chlorine occurs as 35C1 (75.8%) and 37C1 (24.2%); bromine occurs as 79Br (50.7%) and 81Br (49.3%). At what masses do the molecular ions occur for the following formulas? What arc the relative percentages of each molecular ion?

(a) Bromomethane, CH3Br

(b) 1-Chlorohexane, C6H13C1