Evaluation of the Lifetime of Gaseous Ion−Neutral Complexes. 1. A Chemical Activation Study

• Published in: Journal of the American Chemical Society 1998-04, Vol.120 (16), p.3982-3987
• Main Authors: Aschi, Massimiliano, Attinà, Marina, Cacace, Fulvio, D'Arcangelo, Giuseppe
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja964338y

The lifetime of typical ion−neutral complexes (INC) has been evaluated by a chemical activation approach whereby gaseous INC are formed by an exothermic process that imparts them excess internal energy, raising their temperature to T 0, well above the temperature (T) of the bath gas. The hot INC can undergo either prompt reaction at T 0 or thermal reaction at T following collisional deactivation, and the branching ratio of the two processes is deduced from the composition of the products. We have investigated aromatic tert-butylation promoted by addition of toluenium ions to RX neutrals (R = t-C4H9, X = Cl, OH), a reaction that displays a marked temperature dependence of the isomeric composition of the products and, in addition, is known to occur within genuine INC. Following a preliminary study by Fourier transform ion cyclotron resonance and triple quadrupole mass spectrometry, the pressure dependence of the meta/para ratio of the tert-butyltoluenes formed has been investigated by the radiolytic technique in the range from 50 to 4560 Torr in CH4, CH3F and C3H8 at temperatures from 0 to 42 °C.