Browsing by Author "Schöller, Wolfgang W."

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    The donor strength of dialkylamino functions : a systematic study of delta H /HMO pi-electron density correlations in aminobenzenes
    (1978) Effenberger, Franz; Fischer, Peter; Schöller, Wolfgang W.; Stohrer, Wolf-Dieter
    From the resonance interaction between different NR2 substituents and the arylic π-system in mono-,1, 3-bis- and 1,3,5-tris(dialkylamino)benzenes, quantitative parameters are derived for the relative donor strength of the pyrrolidino, dimethylamino, piperidino and morpholino group. Towards an uncharged π-system in the ground state, the donor potential decreases in the series Pyr>N(CH3)2>Pip>Mor. The same order, though with somewhat different gradation, is observed for the aminobenzene/trinitrobenzene charge transfer complex absorptions, and for the polarographic oxidation potentials. The detailed analysis of the chemical shift/π-charge density correlations for methoxy and dialkylamino benzenes also reveals that these substituents exert a significant deshielding effect on protons in ortho-position. This additional downfield shift is probably due to steric interactions and strongly increases from the pyrrolidino to the piperidino group.