Which molecular formula is consistent with the following mass spectrum data? M⁺ ^. at m/z= 84, relative height=10.0%
(M+1) ⁺ ^. at m/z= 85, relative height=0.56%

Question

Which molecular formula is consistent with the following mass spectrum data? M⁺ ^. at m/z= 84, relative height=10.0% (M+1)⁺ ^. at m/z= 85, relative height=0.56%

Quizplus · Accepted Answer

First, we can determine the most abundant ion peak at m/z=84, which corresponds to (M+0)+. This peak indicates the molecular weight of the compound as 84amu. Using the given molecular formula options, only choice B fits this criteria. 
Next, we can use the minor peak at m/z=85 to determine the presence of an isotopic peak, specifically (M+1)+. Choice B also fits this criteria, with the presence of a single 1H atom in the molecular formula accounting for the isotopic peak at m/z=85. None of the other options have a single potential isotopic peak present in their molecular formula.

Which Molecular Formula Is Consistent with the Following Mass Spectrum