Transmission of electronic effects in 4-aryl-2,6-diphenylpyrylium perchlorates and related compounds

• Published in: Journal of physical organic chemistry Vol. 9; no. 9; pp. 631 - 638
• Main Authors: Rasała, Danuta, Bąk, Tomasz, Kolehmainen, Erkki, Styrcz, Stanisław, Gawinecki, Ryszard
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.09.1996
• ISSN: 0894-3230; 1099-1395
• DOI: 10.1002/(SICI)1099-1395(199609)9:9<631::AID-POC829>3.0.CO;2-X

Substituent effects on the 13C NMR spectra of 4‐aryl‐2,6‐diphenylpyrylium and 1‐methyl‐4‐aryl‐2,6‐diphenylpyridinium perchlorates and 4‐aryl‐2,6‐diphenylpyridines were investigated. The dual substituent parameter approach indicates that the resonance contribution to the carbon chemical shifts in the para position to the substituent in the 4‐aryl moiety is comparable to that for 4‐R‐biphenyls. Although heterocyclic moieties jointed at the para position with respect to the substituent in the 4‐aryl group differ in their deactivating power, they diminish the resonance term to the same extent in each series. This may result in conformational variations of the compounds studied. AM1 calculations were used to explain the chemical shifts observed.