A Study of the Styrene Ion-Molecule Reaction by Ion Cyclotron Resonance

Using ion cyclotron resonanee techniques, we have established that structurally different C₈H₈ radical cations are produced by electron impact with styrene and cyclooctatetraene (COT). We have also been able, in this way, to study the ion-molecule reactions occurring in styrene and COT. The styrene radical cation was observed to react with neutral styrene to produce a complex at m/e 208 (C₁₆H₁₆·⁺) which subsequently loses the elements of benzene to form C₁₀H₁₀·⁺ (m/e 130). This is the first example of an observable complex in the bimolecular reactions of olefinic radical cations with neutral olefins. By means of deuterium labeling, ion cyclotron double resonance, and conventional mass spectrometry of suspected intermediates, we have been able to establish the probable structure of the C₁₆H₁₆ ion as 1-phenyltetralin radical cation. Conventional mass spectrometric measurements of the 1-phenyltetralin-4,4-d₂ have established that this compound loses deuteriobenzene almost exclusively via a novel 1,4 elimination to produce an ion at m/e 131. No reaction of C₈H₈ ·⁺ from COT with neutral styrene was found. This investigation shows the utility of ion cyclotron resonanee spectrometry as a means of distinguishing isomeric gas-phase ions.