It is not widely promulgated that the amount of rotation a particular sample gives is wavelength dependent, a phenomenon called optical rotatory dispersion. However, if the X, Y, Z groups are independent, then no chirality is shown. Amines are slower, but still do not permit resolution into two enantiomers. In order to prevent inversion the nitrogen atom has to be part of a three membered ring and also be connected to an atom that has at least one unshared pair of electrons. Restricted rotation about a single double bond is well-known as a potential source of geometric isomerism, though it isn't the only one.
Restricted rotation can also give rise to chirality.
Biphenyls consist of two benzene rings joined by a single bond. If the substituent groups are different, then the molecule will be chiral. Such enantiomers are called atropisomers , and an example is shown at right. Restricted rotation can also be found in spiranes , compounds having two rings with one carbon atom in common. This makes the rings perpendicular, and suitable substitution gives rise to chirality.