Gaseous isomeric Ph-C3H6+ ions: a radiolytic and mass spectrometric study.

Collisional activation mass spectrometry and radiolytic techniques have been used to study the structure, the stability and the interconversion of gaseous C9H+11 ions from different reactions, i.e. (i) protonation of 3-phenyl-1-propene, 2-phenylpropene, cis- and trans-1-phenyl-1-propene, cyclopropylbenzene and indane; (ii) protodehydration and protodehydrohalogenation of Ph-C3H6X (X = OH, Br) substrates; (iii) addition of C3H+5 ions to PhH and of Ph+ ions to propene and cylcopropane. Several model structures have been identified, namely, Ph(Me)2 (a), PhHEt (b), PhCH2HMe (c) and C9H+11 arenium ions from indane. Protonation of cyclopropylbenzene in the presence of MeOH yields exclusively Ph-CH(OMe)Et, which is likely to arise from the cleavage of the protonated, intact C3 ring induced by the attack of the nucleophile. No rearrangement of the linear-chain ions b and c nor of protonated phenylcyclopropane into the branched-chain ion a has been detected under chemical ionization conditions, nor in the radiolytic systems, while significant c → b isomerization occurs in the period of time, ca. 10−8 s, required for the capture of the ionic intermediates by the nucleophile.