Hindered rotation about C–N bonds: equilibration of diastereomeric rotational isomers

The equilibration of diastereomeric rotational isomers of 4,6-diamino-1,2-dihydro-2-methyl-1-(o-tolyl)-s-triazine hydrochloride (I), and 5-methyl-3-α-naphthyl-2-thiohydantoin (II) has been followed by integration of their n.m.r. spectra, and the activation parameters for hindered rotation about C–N bonds have been calculated.