Bestimmung von Ringstromanisotropieeffekten im 1H-NMR - Spektrum von 9-Phenylderivaten des 1.4-Dimethylanthracens und 1.4-Dimethyltriptycens / Determination of Ring Current Anisotropy Effects in the 1H NMR Spectra of 9-Phenyl Derivatives of 1,4-Dimethylanthracene and 1,4-Dimethyltriptycene

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Abstract
The 1,4-Dimenthyl-9-antliracenyl group is useful as a ring current probe for a 9-phenyl substituent. The splitting between the 1- and 4-methyl group signals due to the diamagnetic ring current anisotropy of the 9-phenylring is 0.84 ppm (0.85 ppm in 9-mesityl- 1,4-dimethylanthracene and 0.86 ppm in 9-phenyl-l,4,6,7-tetramethylanthracene), much larger than in phenylmesitylene (0.32 ppm). In 9-phenyl-1,4-dimethyltriptycene the splitting is reduced to 0.55 ppm due to the change in geometry. By use of an assumed geometric model for all four compounds the magnitude of the splitting could be predicted with a maximum deviation of 0.09 ppm using the tables of Haigh and Mallion. As effective magnetic location for the methyl group the midpoint of the basis of the CH3 cone was chosen. In 9-phenyl-1,4,5,8-tetramethyltriptycene the 9-phenyl ring is not orientated perpendicular but parallel to the 1,8-methyl groups and as the analysis of the ABCX-spin-spin system of the unsubstituted phenyl ring shows tilted by about 24 ° away from the 1,8- methylgroups.

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