title: Superacid-promoted ionization of alkanes without carbonium ion formation: a density functional theory study.
abstract: The carbonium ion has been suggested to be the intermediate in superacid-promoted reactions (SbF(5)-HF) such as hydrogen-deuterium exchange and in the electrophilic C-H cleavage into hydrogen and the carbenium ion. In this study, the superacid-promoted C-H cleavage into hydrogen and the carbenium ion was studied using density functional theory (B3LYP and M062X) and ab initio methods (MP2 and CCSD). The calculations suggest that the superacid-promoted C-H cleavage proceeds via a concerted transition state leading to hydrogen (H(2)) and the carbenium ion without the formation of the elusive carbonium ion. The reactivity for the superacid-promoted C-H cleavage decreases upon going from isobutane (tertiary) > propane (secondary) > isobutane (primary) > propane (primary) > ethane >> methane.
authors.affiliation: Department of Chemistry-BMC, Uppsala University, Box 576, S-751 23 Uppsala, Sweden. peter.diner@kemi.uu.se
authors.forename: Peter
authors.initials: P
authors.lastname: Dinér
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D000965:Antimony / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry*; D006858:Hydrofluoric Acid / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D000473:Alkanes; C529140:antimony pentafluoride; D000965:Antimony; D005459:Fluorides; D006858:Hydrofluoric Acid