Isotopomer Distributions of Neutral Products from a Doubly Labeled Cation in the Gas Phase. Interconversion of 1-Fluoro-1-propyl Cation and 1-Fluoroisopropyl Cation on the C3H6F+ Potential Energy Surface

Article abstract of DOI:10.1021/ja00018a009

The title cations CH3CH2CHF⁺ (3) and CH3CHCH2F⁺ (4) are formed as transient intermediates in the gas phase.These are labile on the millisecond timescale as free ions but can be intercepted in ion-neutral complexes.When 3 is generated as free cation by reaction of CF3⁺ with propionaldehyde, it rearranges to (CH3)2CF⁺ (1), as shown by recovery of 2-fluoropropene as a neutral product from its deprotonation in an EBFlow experiment.The same neutral product is recovered when 1 is produced directly by reaction of acetone with CF3⁺ in the EBFlow.Neutral productsindicative of 3 and 4 (allyl fluoride and 1-fluoropropene) are recovered when these cations are formed in + PhO^.> ion-neutral complexes by electron bombardment of CH3CDFCH2OPh (6).Analysis of the isotopic distribution in the recovered neutrals from EBFlow radiolysis of CH3CDF^*CH2OPh (where the asterisked carbon is 13C-labeled) allows an assessment of the primary rearrangement pathways.The distribution of label is assayed by using 19F NMR.Rearrangement of the R⁺ moiety to form deuterated 1 occurs in about half of the complexes formed.In the remainder, methyl transfer (to form deuterated 3) is 2-3 times faster than fluoride transfer (to form deuterated 4).Scrambling of deuterium in the neutral products provides evidence that 3 and 4 interconvert within the ion-neutral complexes.