Chemistry of nuclear recoil¹⁸f atoms. v. mechanism and systematics in ch₃cf₃

Nuclear recoil ¹⁸F atoms undergo hot F-for-F and F-for-H atomic substitution and hot F-for-CH₃ and F-for-CF₃ alkyl replacement reactions in CH₃CF₃. The primary absolute yields corresponding to these processes are 3.56±0.07, 8.22±0.09, 5.79±0.31, and 8.5±2.5% (estimated value), respectively. The total primary hot yield for organic products is 26.1±2.5%, and that for all hot reactions including F-to-HF and F-to-F₂ abstraction is 83±3%. There is no evidence in favor of hot F-for-2F or F-for-2H double substitution reactions in CH₃CF₃. Recoil ¹⁸F exhibits approximately a sixfold systematics preference for alkyl replacement reactions at the carbon-carbon bond in CH3CF3 relative to the average of substitution reactivities at carbon-fluorine and carbon-hydrogen bonds. The per-bond preference for primary substitution reactions at carbon-hydrogen relative to carbon-fluorine bonds is 2.30±0.06. The sums of primary hot yields for organic products are comparable for recoil 18F in CH3CF3 vs recoil 3H in alkanes, so that these two recoil systems differ principally in that ¹⁸F exhibits a preference for alkyl replacement reactions, whereas recoil ³H exhibits a preference for T-for-H substitution. All the organic products from primary ¹⁸F hot reactions exhibit extensive unimolecular decomposition.