The barrier to rotation about the aryl-carbonyl bond in 40 tertiary aromatic amides was determined by variable temperature NMR spectroscopy (for rapid rotations) or by following the interconversion of atropisomers (for slower rotations). Empirical guidelines to the rate of Ar CO bond rotation in hindered tertiary aromatic amides, and hence the stability of the atropisomeric stereoisomers of axially chiral amides, are presented.
