Fig. 2.

Illustration of torsion angles for a group of substituted bi-phenyl ring system. The torsion angles increase with increasing bulkiness of the substituents in the following order: H < F < OH < Cl < Me. The bi-phenyl ring systems are of the smallest torsion angles (37–45^o) when they are unsubstituted or substituted with small atoms such as fluorine or oxygen. Chloride or 2-methyl substituted bi-phenyl ring systems exhibit moderate torsion angles (54–65^o). The torsion angles of the 2, 2’-dimethyl substituted biphenyls are further increased (78–87^o). Reproduced with permission from Lai et al. (47)