ISSN:
0749-1581
Keywords:
Rotational barriers
;
1H NMR spectra
;
Partial double bond character
;
Mesomerism in pyrylium and thiopyrylium salts
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The 13C NMR spectra and variable-temperature 1H NMR spectra of some NR2-substituted pyrylium and thiopyrylium salts were studied, and the rotational barriers thus obtained about the exocyclic partial C—N double bonds are discussed according to their dependence on the counter anion and other structural variations. The counter anion has a negligible influence on the barrier, but substituents on the ring can either strengthen electronically or weaken sterically the mesomerism of the NR2-heteroaromatic system. The competition between these two effects is readily estimated from the rotational barriers obtained. The pyrylium salts display higher rotational barriers than the identically substituted thiopyrylium salts.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260270802
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