Rearrangements in the mass spectra of α‐phenylcinnamic acid and its derivatives

The electron impact ionization and collisional activation mass spectra of α‐phenylcinnamic acid and its derivatives have been studied. The loss of a phenylic hydrogen is not an important process in these molecules, unlike the unsubstituted cinnamic acids. However, in o ‐chloro‐α‐phenylcinnamic acid and its methyl and trimethylsilyl derivatives loss of Cl resulting in the formation of 2‐substituted‐3‐phenylbenzopyrilium ion is an important fragmentation pathway. The rearrangement ions observed at m / z 118 and 107 in the Spectrum of α‐phenylcinnamic acid have been found to have the structures of the M + ˙ of benzofuran and PhCH \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^{\rm +} $\end{document} H, respectively. The ion at m / z 121 in the spectrum of the methyl ester of α‐phenylcinnamic acid has been found to have the structure PhCH \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^{\rm +} $\end{document} Me.