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Charge Dispersal in the Quinuclidine Radical Cation and in the Quinuclidinium Ion, as Revealed by PE and ICR Spectroscopy
Author(s) -
Heilbronner Edgar,
Honegger Evi,
Lecoultre Jacques,
Grob Cyril A.,
Houriet Raymond,
Rolli Eric
Publication year - 1986
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19860690836
Subject(s) - chemistry , quinuclidine , protonation , ion , ionization , gas phase , proton affinity , solvent , spectroscopy , basis set , ionization energy , computational chemistry , molecule , analytical chemistry (journal) , stereochemistry , organic chemistry , physics , quantum mechanics
The n N −1ionization energies I 1 cand the gas‐phase basicities GB of CH 3 ‐, Cl‐, or CN‐substituted quinuclidines have been measured by PE and ICR spectroscopy. The dependence of the shifts ΔI 1 cand Δ GB (relative to the values of the parent molecule) allow conclusions about the charge dispersal accompanying the n N −1ionization or the protonation of quinuclidine in the gas phase. The agreement with the results of a minimal basis set ab initio calculation is excellent. Comparison of the solution p K a values with either I 1 cor GB reveals that 2‐substituted quinuclidines exhibit sizeable solvent‐induced proximity effects, i.e. that the corresponding quinuclidinium ions are more acidic in solution than expected on the basis of the gas‐phase basicities. This agrees with earlier results concerning 2‐substituted pyridines.