Gas-phase halonium metathesis and its competitors. Skeletal rearrangements of cationic adducts of saturated ketones. - Archive ouverte HAL Access content directly
Journal Articles Journal of the American Chemical Society Year : 2002

Gas-phase halonium metathesis and its competitors. Skeletal rearrangements of cationic adducts of saturated ketones.

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Abstract

The methyl cation and CF(3)(+) attack saturated, acyclic ketones to make vibrationally excited adduct ions. Despite their high internal energies and short lifetimes, these adducts undergo deep-seated rearrangements that parallel slower processes in solution. Observed pathways include alkene and alkane expulsions, in addition to (in the case of CF(3)(+)) the precedented loss of CF(2)O + HF. For the vast majority of ketones, the principal charged products are the CF(3)(+) adducts of lighter carbonyl compounds, ions that are not easily prepared by other avenues. Evidence for ion structures comes from collisionally activated unimolecular decomposition and bimolecular ion-molecule reactions. Typical examples are di-n-propyl and diisopropyl ketones (both of which produce CH(3)CH=OCF(3)(+) as the principal ion-molecule reaction product) and pentamethylacetone (which produces (CH(3))(2)C=OCF(3)(+) as virtually the sole ion-molecule reaction product). Isotopic labeling experiments account for mechanisms, and DFT calculations provide a qualitative explanation for the relative abundances of products from unimolecular decompositions of the chemically activated CF(3)(+) adduct ions that are initially formed.

Dates and versions

hal-00918093 , version 1 (13-12-2013)

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P. Mayer, Danielle Leblanc, T. Morton. Gas-phase halonium metathesis and its competitors. Skeletal rearrangements of cationic adducts of saturated ketones.. Journal of the American Chemical Society, 2002, 124 (47), pp.14185-14194. ⟨10.1021/ja020557+⟩. ⟨hal-00918093⟩
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