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13 C NMR spectroscopy of heteroaromatic compounds: A quantitative measure of electron deficiency and excessiveness
Author(s) -
Paudler William W.,
Jovanovic Misa V.
Publication year - 1982
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270190407
Subject(s) - pyridazine , pyrazine , furan , chemistry , thiophene , benzene , pyridine , reactivity (psychology) , electrophile , triazine , pyrimidine , chemical shift , medicinal chemistry , nuclear magnetic resonance spectroscopy , organic chemistry , stereochemistry , catalysis , pathology , medicine , alternative medicine
A quantitative measure, π Δ, for expressing the π‐deficiency and π‐excessiveness of heteroaromatic compounds has been developed through 13 C NMR chemical shift studies. An example which correlates electrophilic reactivity in π‐excessive systems with π Δ of these compounds is given. The following decreasing order of π‐excessiveness and increasing π‐deficiency of a number of heteroaromatic systems has been established (numbers in parentheses correspond to π Δ): tellurophene (1.83), selenophene (1.43), thiophene (1.35), furan (1.31), benzene (1.00), pyrazine (1.00) pyridine (0.89), pyrimidine (0.77), pyridazine (0.71), 1,2,4‐triazine (0.64). These correlations also allow the prediction of 13 C chemical shifts in substituted heteroaromatic compounds, where the ratio of the difference between a given substituted heterocyclic compound and its parent, and the identically substituted benzene derivative, has been determined.