CARBON-13 MAGNETIC RESONANCE .14. AZA-ANALOGS OF POLYCYCLIC AROMATIC HYDROCARBONS

The carbon-13 chemical shifts for naphthalene and anthracene along with some of their mono and diaza analogs are reported. Additive relationships between structural features and these chemical shift values were found, and these provide a highly reliable method for making spectral assignments. Quantum mechanical treatments of the chemical shift data were used to rationalize shift values in terms of the paramagnetic screening mechanisms. Using EHT and CNDO wave functions, these calculations characterized certain types of weaknesses in these approximate treatments, and some modifications were suggested for improving the wave functions. It is concluded that inductive and resonance effects expected for this class of compounds are adequate to account for the principle variations noted in the carbon-13 chemical shift data. Furthermore, the agreement supports the position that the simple wave functions for these relatively large molecules are faithfully accounting for the essential features of the electronic structure. © 1969, American Chemical Society. All rights reserved.