title: The strongest Brønsted acid: protonation of alkanes by H(CHB(11)F(11)) at room temperature.
abstract: What is the strongest acid? Can a simple Brønsted acid be prepared that can protonate an alkane at room temperature? Can that acid be free of the complicating effects of added Lewis acids that are typical of common, difficult-to-handle superacid mixtures? The carborane superacid H(CHB11 F11 ) is that acid. It is an extremely moisture-sensitive solid, prepared by treatment of anhydrous HCl with [Et3 SiHSiEt3 ][CHB11 F11 ]. It adds H2 O to form [H3 O][CHB11 F11 ] and benzene to form the benzenium ion salt [C6 H7 ][CHB11 F11 ]. It reacts with butane to form a crystalline tBu(+) salt and with n-hexane to form an isolable hexyl carbocation salt. Carbocations, which are thus no longer transient intermediates, react with NaH either by hydride addition to re-form an alkane or by deprotonation to form an alkene and H2 . By protonating alkanes at room temperature, the reactivity of H(CHB11 F11 ) opens up new opportunities for the easier study of acid-catalyzed hydrocarbon reforming.
authors: Center for s and p Block Chemistry, Department of Chemistry, University of California, Riverside, CA 92521 (USA) http://reedgrouplab.ucr.edu/; Current address: Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139-4307 (USA).
authors: Matthew
authors: M
authors: Nava
authors: Irina V
authors: IV
authors: Stoyanova
authors: Steven
authors: S
authors: Cummings
authors: Evgenii S
authors: ES
authors: Stoyanov
authors: Christopher A
authors: CA
authors: Reed
keywords: Brønsted acids; carbocations; carboranes; hydrocarbons