The unsubstituted phenyl ring in ketazolam, a 1,4-benzodiazepine derivative, has a two-fold rotational barrier about the aryl to tert-alkyl bond connecting this phenyl group to the rest of the molecule. At 50.3 MHz, all twenty of the13C resonances of ketazolam are resolved below -40°C, including two distinct resonances for theorthocarbons and two for themetacarbons. Twelve of the twenty13C nuclei resonate between 138 and 125 ppm, necessitating assignment via a combination of one-bond and long-range heteronuclear shift correlation experiments.