Abstract
Cyclophanes are the compounds in which more than two atoms of an aromatic ring are incorporated into a medium or large ring system. Cyclophanes have highly strained molecular structure with abnormal physical properties and chemical reactivities. Molecular structures of wide variety of para and metacyclophanes have been determined by X-ray diffraction since the discovery of (2.2) paracyclophane by Brown in 1949. Unusual physical properties investigated by NMR and UV spectra were interpreted in terms of strained molecular structure and transannular interaction of π-electrons of benzene rings. Experimental measurement and theoretical treatment using empirical valence-force potentials were made to estimate the strain energy of cyclophanes quantitatively.
