Fast Interconversion of C4H7+ Cations in the Gas Phase and in a Gaseous Microsolvated Environment

The equilibration of cyclobutyl 1 and 1′ and the cyclopropylmethyl cation (2) has been studied in the gas phase by utilizing FT-ICR mass spectrometry and high-pressure radiolytic techniques. A suitable gaseous nucleophile, C6X6 (X=H,D), was used to sample the equilibration of C4H7+ ions, produced from both cyclobutanol and cyclopropylmethanol. These are either dispersed in the bulk gas or confined within a C4H7+/C6X6 complex that contains a molecule of solvent (H2O). The analysis of the products shows that, irrespective of their source and of the intermolecular or intracomplex nature of the process, the C4H7+ ions undergo equilibration before they are trapped. The equilibrium (1+1′)/2 ratio is very close to unity at 300 K, and the results from the intracomplex trapping experiment show that equilibration occurs within a time interval ≤10−10 s.