13C NMR and force field investigations of hydrindane conformations

Abstract
13C NMR shifts of trans‐ and cis‐annelated bicyclo[4.3.0]nonanes with substituents R in position 8 (R  H, OH, Cl, Br) and 1‐hydroxy derivatives were analysed on the basis of force field calculated torsional angles using Allinger's MM1 program. Shielding increments for the 6 membered ring agree with corresponding cyclohexane values within ± 0.8 ppm maximal deviation. 13C NMR line shape analysis with cis‐hydrindane between 148 and 180 K yielded ΔH* = 37.0 ± 0.4 kJ mol−1 and ΔS* = 28 J mol−1 K−1 for the topomerization. The force field calculated reaction profile showed ΔH* = 37 kJ mol−1, in close agreement.