Bicyclo heptane, mass spectrum

Applying these pieces of information to the mass spectrum of bicyclo[2.2.1]heptane (Fig. 8.11), we can identify fragment peaks due to the loss of the side chain (the one-carbon bridge, plus an additional hydrogen atom) at mie = 81 and the loss of ethene at m/e = 68. The fragment ion peak at m/e = 61 is due to the loss of ethene plus an additional hydrogen atom. 

FIGURE 4.12 El mass spectrum of bicyclo[2.2.1]heptane (norbomane). 

---