(1) Lehrkanzel für Organische Chemie der Universität Wien, Währinger Straße 38, A-1090 Wien, Österreich
Abstract:
From racemization studies on optically active 2.2]metacyclophanes substituted in position 4, the parameters of activation for the inversion of the tenmembered ring were found to be: G423
=31.5 kcal/mole, H=27.5 kcal/mole and S=–10 Cl/mole.Racemization does not occurvia bond forming or breaking; the value for the inversion barrier is not affected by substituents in position 4 and therefore corresponds to the value of unsubstituted 2.2]metacyclophane, whereas substituents in the bridge exert a distinct influence. These results can easily be explained on the basis of the isoconformational concept.Mit 5 AbbildungenHerrn Prof. Dr.O. Hoffmann-Ostenhof mit besten Wünschen zum 60. Geburtstag gewidmet.