A detailed study of the kinetics, thermodynamics and mechansim of carbon-carbon bond fragmentation in a series of aminoalcohol radical cations is presented. The compounds that provide the basis for this investigation are derived from the parent structure, erythro-2-(phenylamino)-1,2-diphenylethanol, by substitution at the para position of the N-phenyl with methoxy, methyl, (hydrogen), chloro, and cyano groups (compounds 1a-e, respectively). The rates for C-C bond fragmentation for radical cations 1a-e(.+) in CH3CN solution were determined by laser flash photolysis and vary from 3.9 x 10(4) (1a) to 7.4 x 10(6) s(-1) (1e). The activation parameters for bond fragmentation in Ic-e(.+) are characterized by low activation enthalpies and relatively large, negative activation entropies. The bond fragmentation rates increase with the peak potential for anodic oxidation of the neutral aminoalcohols, E(p)(1). Correlation of the free energy of activation for bond fragmentation (Delta G(BF)double dagger) with FE(p)(1) (F is the Faraday constant) implies that the dependence of Delta G double dagger(BF) on Delta G degrees(BF) is relatively weak, consistent with bond fragmentation in 1a-e(.+) being weakly endothermic or exothermic. The transient absorption spectra of the reactive intermediates produced by fragmentation of 1a-e(.+) are consistent with a mechansim involving heterolytic fragmentation of the C-1-C-2 bond with concomitant loss of the hydroxyl proton. By contrast, FT-ICR studies of 1a-e(.+) indicate that in the gas phase homolytic fragmentation of the C-1-C-2 bond predominates. Semiempirical calculations using the AM1 Hamiltonian demonstrate that in the gas phase homolysis is the thermodynamically preferred pathway, consistent with the FT-ICR results.