ISSN:
0030-4921
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
A quantitative measure, πΔ, for expressing the π-deficiency and π-excessiveness of heteroaromatic compounds has been developed through 13C NMR chemical shift studies. An example which correlates electrophilic reactivity in π-excessive systems with πΔ 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 πΔ): 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 13C 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.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1270190407
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