Effects of substitution on nitrogen on barriers to rotation of cyclic amides. Part I. Investigation of the rotational barier in 4-benzoyl-1-thia-4-azacyclohex-2-ene by 1H dynamic nuclear magnetic resonance spectroscopy

Abstract

The rotational barrier in 4-benzoyl-1-thia-4-azacyclohex-2-ene has been investigated by total line-shape analysis of variable temperature ¹H nmr spectra in acetonitrile-d₃. Separate treatment of the vinyl and methylene signals yielded sets of values for activation parameters which were in excellent agreement. Assignment of the major and minor rotational isomers was made from chemical-shift data derived from the ¹³C nmr spectrum at 243 K in acetonitrile-d₃.