Proton chemical shifts in triphenylene and methyltriphenylenes

Abstract

For triphenylene and methyltriphenylenes, calculations have been made of the approximate shieldings to be expected for ring and methyl hydrogens as a result of ring currents and σ-bond anisotropies. Agreement of these calculations with observed shifts is good for both “bay” and “peninsular” protons in triphenylene and for “peninsular” methyl groups in methyltriphenylenes. For bay methyl protons, however, the calculated deshielding is appreciably larger than that found experimentally, and a secondary proximity effect is proposed.