CCSD(T)-F12a study of reactions of interstellar anions C2nH-(n = 2-4) with HCCH.
Explicitly correlated coupled cluster theory at the CCSD(T)-F12a level (Adler, T. B.; Knizia, G.; Werner, H.-J. J. Chem. Phys. 2007, 127, 221106) was employed to study the energetics of reactions of interstellar anions C(2n)H(-) with HCCH, which may formally be regarded as proton-transfer reactions. The gas-phase acidities at 0 K for the polyynes HC(2n)H with n = 2-4 are predicted to be 1516.5, 1483.2, and 1462.6 kJ mol(-1). The energy profiles of the collinear reactions are characterized by absolute minima corresponding to the hydrogen-bonded species HC(2n)(-)...HCCH, saddle points at which the proton is shared between the two anion moieties, and a second minimum in the exit channel of the reaction, which becomes less pronounced with increasing n.
Botschwina
Peter
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Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, D-37077 Göttingen, Germany. pbotsch@gwdg.de
Oswald
Rainer
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