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Published June 1, 1978 | public
Journal Article

Steric and Electronic Effects on ^(15)N Chemical Shifts of Piperidine and Decahydroquinoline Hydrochlorides

Abstract

Natural-abundance ^(15)N NMR chemical shifts of a number of closely related C- and N-methyl-substituted piperidine and decahydroquinoline hydrochlorides have been measured in chloroform and methanol. For each solvent, the ^(15)N shifts of the salts of secondary and tertiary amines give different linear correlations with the ^(13)C shifts of the corresponding carbons of their hydrocarbon analogues. Additive shift parameters as well as protonation-shift parameters for carbon substitution near nitrogen have been determined. Three of the nine parameters have a pronounced solvent dependence. The substituent-shift parameters for hydrochlorides are in general closer to the analogous values for ^(13)C NMR than the corresponding parameters which correlate the I5N shifts of the free amines. The parameters for substitution on @carbons are an exception. The ^(13)C shifts of some of the compounds can be used to elucidate conformational questions.

Additional Information

© 1978 American Chemical Society. Received August 12, 1977. We wish to thank Professor M. Allen for providing a very useful computer program doing least-squares multilinear regression analysis, and Professor K. L. Williamson for preparing and measuring the shifts of 8-(e)-methyltrans-decahydroquinoline. We are also indebted to Dr. André Gagneux of Ciba-Geigy AG, Basel, who provided a sample of 2-azaadamantane, to Professor Robert T. LaLonde of the College of Environmental Science and Forestry, State University of New York at Syracuse, for the sample of 3-methylquinolizidine, and to Dr. D. K. Dalling of the University of Utah for calculations of ^(13)C chemical shifts of decalins. Supported by the National Science Foundation, and by the Public Health Service, Research Grant GM-11072 from the Division of General Medical Sciences.

Additional details

Created:
August 19, 2023
Modified:
October 24, 2023