Ring orientation in  -ionone and retinals.
The ring orientation in beta-ionone, all-trans retinal, and 11-cis retinal, relative to that of the polyene chain, has been determined by means of semi-empirical calculations and magnetic resonance measurements of the nuclear Overhauser effect and long-range coupling constants. The experimental results yield a distorted s-cis conformation about the C(6)-C(7) "single bond", with the torsional angle in the range 30 degrees to 70 degrees . This agrees well with the semi-empirical potential function, which has a broad, rather flat minimum for angles from 40 degrees to 120 degrees . The temperature dependence of the NMR results provide confirmation for the form of the torsional potential.
D002074:Butanones / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D008433:Mathematics; D008961:Models, Structural; D011487:Protein Conformation; D012168:Retinal Pigments / Q000032:analysis*
D002074:Butanones; D012168:Retinal Pigments