Konfigurationen und Konformationen von zwei 2,4,6,8-Tetrabrom-cyclooctan-1, 5-dionen

The two isomeric tetrabromides, α-isomer mp. 198° and β-isomer mp. 226° described in 1], are identified as cis, cis, trans-2, 4, 6, 8-tetrabromo-cyclooctane-1, 5-dione ( 2 ) and cis, trans, cis-2, 4, 6, 8-tetrabromo-cyclooctane-1, 5-dione ( 3 ) by an analysis of their NMR.-spectra which also allows a derivation of their preferred conformations. Both exist in solution as boat-chair conformers, the geometries of which correlate well with the IR.- and UV.-spectra.