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Calculation of the nitrogen screening constants of some N-heterocycles

✍ Scribed by K. A. K. Ebraheem; G. A. Webb; M. Witanowski

Publisher: John Wiley and Sons
Year: 1978
Tongue: English
Weight: 316 KB
Volume: 11
Category: Article
ISSN: 0749-1581
DOI: 10.1002/mrc.1270110107

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✦ Synopsis

Absolute nitrogen screening constants and chemical shifts of some N-heterocycles are calculated within the CNDO/S level of approximation to Pople's model. Satisfactory agreement between calculated and observed nitrogen chemical shifts is obtained in most cases. The application of the results to the study of tautomeric equilibria is discussed. 'Pyridine-type' nitrogen chemical shifts are dominated by n + m* transitions together with significant contributions from m -+ u* and u -+ m* transitions whereas the latter two are the dominant ones for 'pyrrole-type' nitrogen nuclei.

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