Chapter 16, Problem 16.74P

Interpretation Introduction

(a)

Interpretation:

The structures of the species that correspond to each of the peaks A–E in the given mass spectrum of heptane is to be drawn.

Concept introduction:

The mass spectrum of a compound is often represented as a bar graph with m/z on the x axis (where m is in atomic mass units, u) and the relative abundance of ions at each m/z on the y axis. The mass of each ion is just the mass of the atoms that make it up. The ${\text{M}}^{\text{+}}$ peak of a mass spectrum is taken to be the compound’s molecular mass. Each fragmentation produces a cation and an uncharged species, ensuring that the total charge after fragmentation is the same as it was before fragmentation. When a molecular ion undergoes fragmentation, there must be conservation of charge. A molecular ion whose charge is +1 invariably fragments into one species bearing a +1 charge and another that is uncharged.

Interpretation Introduction

(b)

Interpretation:

The ${\text{M}}^{+}$ peak, the $\text{M+1}$ peak, and the base peak are to be identified.

Concept introduction:

The ${\text{M}}^{\text{+}}$ peak of a mass spectrum is taken to be the compound’s molecular mass. The base peak is the peak with the highest intensity.