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This study supplements earlier research (Molina et al) with new experimental findings on stilbene and two stilbene derivatives in which ethano or methylene bridges prevents rotation around the vinyl-phenyl bonds.

A study aiming to resolve the debate on the molecular symmetry of [2,2]paracyclophane presents the results of highly correlated ab initio calculations that predict a distortion to D2 symmetry in accordance with experimental data. The structure of the cyclobutane ring was scrutinized at various levels of theory to select an appropriate chemical technique for the description of this phenomenon. Results of the study are discussed.

The vibrational analysis by Walden et al. of the [2,2]paracyclophane using density functional calculations is problematic. The study involved conducting unrestricted structure optimization that resulted in a local minimum with D2 symmetry. One of the problems with the study concerns the twist angle of the aromatic rings. Another is the height of the barrier between the two degenerate D2 conformers.