Conformation and stereodynamics of alkyl 9-anthryl sulfoxides

Several alkyl 9-anthryl sulfoxides exhibit broadening of the aromatic peri-proton signal in 1H NMR spectra recorded at ambient temperature due to hindered rotation about the 9-anthryl–sulfur bond; the rotational barriers lie in the range 10.9–18.9 kcal mol–1. The preferred conformation and torsional barriers in these sulfoxides and in mesityl methyl sulfoxide have also been investigated by molecular mechanics calculations.