SYNTHESIS AND STUDY OF PSEUDOAROMATIC COMPOUNDS .X. A REEVALUATION OF QUESTION OF AROMATIC CHARACTER IN TROPONE, TROPOLONE, AND SUBSTITUTED HEPTAFULVENES BASED ON ANALYSIS OF NUCLEAR MAGNETIC RESONANCE SPECTRA OF THESE AND SEVERAL RELATED COMPOUNDS

Analyses of the nmr spectra of tropone, 2-chlorotropone, tropolone, tropolone 2-methyl ether, 5,6-benzotropolone, 1,3-dideuterioazulene, 2-indenyltropenium ion, the conjugate acid of tropone, methoxytropenium ion, 8,8-dicyanoheptafulvene, 3,3-dimethyl-2-cycloheptatrienylideneindanone, cyclohepta-2,4-dienone, 2-methyl-styrene, 6-dichloromethy1-6-methylcyclohexa-2,4-dienone, and the conjugate acid of 6-dichloromethyl-6-methyl-cyclohexa-2,4-dienone are reported. Correlation of the coupling constants of these compounds and those of several related systems indicates that tropone, tropolone, and 8,8-dicyanoheptafulvene exhibit bond alternation characteristic of polyenones and polyenes, and thus do not exhibit appreciable aromatic character. © 1969, American Chemical Society. All rights reserved.