In-Methylcyclophane

[1] This particular compound is synthesed starting from anthracene with a methyl group added to each arene ring (1,8,9-trimethylanthracene).

Next the methyl substituents are functionalized with bromine groups by the photochemical reaction with N-bromosuccinimide or NBS.

X-ray crystallography of the tri-sulfone derivative of this cyclophane shows that the methyl group located 289.6 picometers from the center of the benzene ring.

The carbon-to-carbon bond linking the methyl group to the triptycene frame is actually shortened and measures 147.5 to 149.5 pm.

The reason for this anomaly is that the methyl protons are in line with the aromatic ring current of the benzene ring and are therefore severely shielded, an effect similar to the nucleus-independent chemical shift method of analyzing aromaticity.