Conformational impact of pentafluorosulfanylation on acyclic aliphatic molecules

Abstract The diastereotopic nature of geminal protons γ to the pentafluorosulfanyl (SF 5 ) group was investigated by computational modeling and experimental methods. 1D and 2D NMR techniques were employed to determine the vicinal coupling constants used in the estimation of H C C H dihedral angles required for the approximation of the average solution conformation of SF 5 -substituted alkyl chains. Rotational energy barriers were calculated at the B3LYP/6-31++G (d,p) level in an effort to assess the relative steric demand of the SF 5 group relative to a trifluoromethyl or tert -butyl group. The observed diastereotopicity is likely a result of hindered molecular rotation where one of the γ protons is trapped between two equatorial fluorines of the SF 5 group.