A tandem mass spectrometric investigation of (C2H5)2X+ ions (X = Cl,Br, I): The involvement of classical and nonclassical ethyl structures therein

The formation of diethyl halonium ions (C₂H₅)₂X⁺ (X = Cl, Br, I) by a variety of ion-molecule reactions is described. The dissociation characteristics (metastable and collision-induced dissociation mass spectra) of these ions and their isomers were studied in detail. Some of the neutral fragmentation products were examined by their collision-induced dissociative ionization mass spectra. The participation of classical (1, CH₃CH₂X⁺CH₂CH₃) and nonclassical forms of the ions was considered. Dissociation reactions for which loss of positional identity of H-D atoms took place, for example C₂H₄ loss (a common fragmentation of metastable ions) and C₂H₅ ⁺ formation, were interpreted as involving nonclassical ions, 2. It was concluded that the ion-molecule reactions produced both ion structures, but in different halogen-dependent proportions. For (C₂H₅)₂C1⁺ ions, 2 is the major species, for (C₂H₅)₂Br⁺ both 1- and 2-type ions are generated, whereas for (C₂H₅)₂I⁺ the classical form 1 must be the predominant structure.