NUCLEAR MAGNETIC RESONANCE SPECTRA OF CYCLOHEXA-2,5-DIEN-1-ONE SYSTEM (PARA-DIENONES

Proton and fluorine NMR. spectra of several para‐dienones (4‐allyl‐4‐methyl‐cyclohexa‐2,5‐diene‐1‐one and its 2‐ and 3‐fluoro derivatives, a spirocyclic bis‐dienone and two dienone alkaloids) have been analysed using multiple resonance, solvent effects, and computer techniques. The relative signs of all the H, H‐ and H, F‐coupling constants of the para‐dienone system have been determined. The nature and significance of long range coupling in cyclic and openchain cross‐conjugated dienones is discussed in comparison with related systems of aromatic character. Copyright © 1969 Verlag GmbH & Co. KGaA, Weinheim