Chapter G, Problem G.3P

Interpretation Introduction

Interpretation:

A peak appears at m/z = $83$ in the mass spectrum of $\text{hept-3-ene}$. The fragmentation of $\text{hept-3-ene’s}$ molecular ion produces the ion that gives rise to this peak is to be shown. The reason we think the peak at m/z = $83$ is smaller than the one at m/z = $69$ is to be explained.

Concept introduction:

The mass of $\text{hept-3-ene}$ is $\text{98}$ u. The $\text{π}$- electron of the $\text{C-C}$ bond is ejected in the ionization process to produce the molecular ion. $\text{Hept-3-ene}$ is not symmetrical, and there are two allylic $\text{C-C}$ bonds, so fragmentation can happen via two routes.