An experiment to determine the rotational barrier about a C[subscript aryl]-N[subscript imide] single bond that is suitable for first-semester organic chemistry students is presented. The investigation begins with the one-step synthesis of a N,N'-diaryl naphthalene diimide, which exists as two room temperature-stable atropisomers (syn and anti). The students then estimate the rotational barrier, [Delta]G[double dagger], by following the reequilibration of the two isomers using two-dimensional thin-layer chromatography. A more accurate determination of the rotational barrier is conducted by a [to the first power]H NMR time study. The synthesis, purification, and kinetics experiments can be carried out within two, three-hour laboratory sessions using commercially available reagents and instrumentation found in most undergraduate laboratories. (Contains 2 schemes and 3 figures.)