Gas phase reactions of protonated 1,3-diphenylpropyne and some isomeric [C15H13]+ ions

Bäther W, Kuck D, Grützmacher H-F. Gas phase reactions of protonated 1,3-diphenylpropyne and some isomeric [C15H13]+ ions. Organic Mass Spectrometry. 1985;20(9):572-577.Metastable (3-phenyl-2-propynyl)benzenium ions, generated by electron impact induced fragmentation from the appropriately substituted 1,4-dihydrobenzoic acid, react by loss of ·CH3 and C6H6. The study of deuterated derivatives reveals that hydrogen/deuterium exchanges involving all hydrogen and deuterium atoms precede the fragmentations. The results suggest a skeletal rearrangement by electrophilic ring-closure reactions giving rise to protonated phenylindene and protonated 9,10-methano-9,10-dihydroanthracene prior to the elimination of C6H6 and ·CH3, respectively. A study of isomeric [C15H13]+ ions by collision-induced decomposition and by deuterium labelling shows that these ions interconvert by hydrogen migrations and skeletal rearrangements