The standard enthalpies of formation of 1-and 2-Adamantyl cations and radicals. An ab initio study

The results of a G2(MP2) computational study involving 1- and 2-Adamantyl c ations (1(+),2(+)) as well as 1- and 2-Adamantyl radicals (1(.),2(.)) are p resented. They provide purely computational thermodynamic data for the foll owing processes: (i) Ionization of 1(.) and 2(.), (ii) Exchange of hydrogen atoms or hydride anions between Adamantyl radicals or cations and alkyl ra dicals or cations, respectively. These data, once combined with the experim ental enthalpies of formation of iso-C3H7.,iso-C3H7+, tert-C4H9. and tert-C 4H9+. allowed us to screen the available experimental data and to define a self-consistent set of experimentally-based standard enthalpies of formatio n, Delta H-f(m)0. for Adamantyl species, namely: Delta H-f(m)0(1(+),g) = 16 2.0 +/- 2.0; Delta H-f(m)0(2(+),g) = 171.9 +/- 2.0; Delta H-f(m)0(1(.),g) = 17.9 +/- 2.1, Delta H-f(m)0(2(.),g) = 16.6 +/- 2.0 kcal mol(-1). (C) 2001 Elsevier Science B.V. All rights reserved.