Steric effects induced by solvent association. 29Si NMR chemical shifts in trimethylsiloxysteroids controlled by solvent accessible surface

Abstract Chemical shifts of silicon‐29 in 39 trimethylsiloxy derivatives of 5α‐ and 5β‐androstanes reported here satisfy an empirical linear correlation with terms describing molecular geometry. The steric 29Si chemical shifts are controlled by association of the silyl ethers with the hydrogen bonding solvent. The chemical shifts measured in dilute solutions show a dependence on the surface of the oxygen atom accessible to the solvent for hydrogen bonding. The steric upfield shifts are due to steric hindrance to hydrogen bonding which itself produces downfield shifts.