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13C NMR spectra of some halocarbons. Shift predictions in polychloro-quinolines and -isoquinolines

✍ Scribed by R. S. Matthews; M. Jones; J. Banks

Publisher
John Wiley and Sons
Year
1989
Tongue
English
Weight
437 KB
Volume
27
Category
Article
ISSN
0749-1581

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✦ Synopsis

Three methods, two empirical and one semiempirical, for predicting 13C chemical shifts in six plychloroheterocyclics are considered. It was found that the semi-empirical correlations with CNDO/2 calculated charges, although useful, could not be used in isolation from the other two methods. Of these, the MSCS (multiple substituent chemical shifts) method could be used to predict all eighteen carbon shifts in perchloroquinoline and perchloroisoquinoline, whilst the NIMS method (hypothetical nitrogen insertion method) was limited to the carbons in the heterocyclic ring. In brief, it was found that the MSCS method was the most accurate (less than f 1 ppm) for predicting chemical shifts, intrinsically compensating for some of the errors arising from mutual atom-atom interactions.

New 13C data are reported for heptachloroquinolioe, a mixture of two polychloroquinolines, heptachloroisoquinoline and two, separable, new polychloroisoquinolines.

KEY WORDS Polychloroazanaphthalenes Multiple substituent chemical shifts MSCS NIMS 13C predictions

Molecular orbital charge calculations CNDO/2 calculations

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