FLUORINE SHIFTS IN GASEOUS CATIONS - ANALOGS OF WAGNER-MEERWEIN REARRANGEMENTS

In the gas phase ionized (CH3)(2)CFCH(2)OPh (where the asterisk designates a C-13-label) decomposes to yield ionized phenol via two competing pathways, both of which pass through intermediate ion-neutral complexes. One pathway involves methyl shift, which produces complexes that contain 2-fluorobutyl cations. The other pathway involves fluorine transposition, which forms complexes containing fluoro-tert-butyl cations. The distribution of C-13 in the recovered neutral fluoroalkenes confirms that fluorine migration has indeed taken place, and SCF computations point toward a bridged, three-member cyclic transition state. Ab initio calculations provide an ordering of C4H8F+ structures, some of which are isoelectronic with C4H8O epoxy and carbonyl compounds, as well as those that have no stable isoelectronic neutral counterparts.