Restricted Rotation in 9-Phenyl-anthracenes: A Prediction Fulfilled

The calculated phenyl rotation barrier in 9-phenylanthracene has been reported as ∼21 kcal mol−1, but experimental verification of this barrier is limited by its intrinsic symmetry. V-T NMR indicated the barrier to interconversion of the syn (C2v) and anti (C2h) rotamers of 9,10-bis(3-fluorophenyl)anthracene to be ∼21 kcal mol−1. Likewise, the V-T NMR spectra of 9-(1-naphthyl)-10-phenylanthracene reveal that the rotational barrier of the unsubstituted phenyl ring is at least 21 kcal mol−1.