ab i/ifüo-Rechnungen zur relativen Stabilität der Neutralmoleküle, Radikalkationen und -anionen von Allen und Propin / ab initio Calculations on the Relative Stabilities of the Neutrals, Radical Cations and Anions of Allene and Propvne

Abstract

Ab initio calculations demonstrate that, in agreement with experimental results, the oxidation of both allene (1) and propyne (2) to their corresponding cation radicals (1+·nd 2+·) is associated with a reversal of the stability order. Whereas for the neutral molecules 1 is thermochemically less stable than 2 (⊿⊿Hf° = 1.3 kcal/mol) the opposite holds for the cation radicals (1+· is 13.3 kcal/mol more stable than 2+·). The radical anions of 1 and 2 do also show a reversed stability order (1+· being 5.1 kcal/mol more stable than 2-·); however, both radical anions are predicted to undergo spontaneous electron detachement, thus giving their neutral counterparts (negative electron affinities). The changes in geometries and charge distributions associated with the redox reactions of 1 and 2 are briefly discussed