In solvolysis of alkyl halides Hal-(CH2)(n)-C(BCH3)(11)(-)(n = 2, 5, 6, but not 3, 4, or 7) and protonation of alkenes CH2=CH-(CH2)(n-2)-C(BCH3)(11)-(n = 3, 6, 7, but not 4 or 5) carrying the icosahedral electrofuge -C(BCH3)(11)(-) attached through its cage carbon atom, generation of incipient positive charge on C. (as shown in Scheme 1 in the article) leads to simultaneous cleavage of the Cbeta-C(BCH3)(11)(-) bond. The products are a Calpha=Cbeta alkene and a postulated intermediate C+(BCH3)(11)(-) <----> C(BCH3)(11)(-) trapped as the adduct Nu-C(BCH3)(11)(-) by one of the nucleophiles (Nu(-)) present. The reaction kinetics is E1, first order in the haloalky1carborane and zero order in [Nu(-)], and the elimination appears to be concerted, as in the usual E2 mechanism. The process is best viewed as a Grob fragmentation. The loss of the longer chains involves intrachain hydricle transfer from the C-alpha-H bond to an incipient carbocation on C-delta, or C-epsilon, via a five- or six-membered cyclic transition state, respectively. The electronic structure of the postulated intermediate is believed to lie between those of a nonclassical carbonium ylide C+(BCH3)(11)- and a carbenoid C(BCH3)(11) whose electronic ground state resembles the S-2 state of ordinary carbenes.