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Effects of Solvent, Protonation, and N-Alkylation on the ^(15)N Chemical Shifts of Pyridine and Related Compounds

Duthaler, Rudolf O. and Roberts, John D. (1978) Effects of Solvent, Protonation, and N-Alkylation on the ^(15)N Chemical Shifts of Pyridine and Related Compounds. Journal of the American Chemical Society, 100 (16). pp. 4969-4973. ISSN 0002-7863. https://resolver.caltech.edu/CaltechAUTHORS:20151008-070941921

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Abstract

The ^(15)N chemical shift of pyridine has been measured in he gas phase and in a variety of solvents. The solvent-induced resonances are all upfield of the gas phase and correlate qualitatively with hydrogen-bonding capacity. The finding of a reasonable linear correlation with the Kosower 2 values indicates that the solvent shifts are dominated by the contribution of the n→^*π^* transition to the secondary paramagnetic shift term. No correlation was found with either the solvent dielectric constant, є, or the function (є - 1)/(2є + 2.5). Large solvent effects were found for the ^(15)N resonances of pyridine hydrochlorides, and these require that interpretation of protonation shifts be made with care. In contrast to protonation shifts, methylation shifts are essentially solvent and counterion independent. The changes in ^(15)N chemical shifts of 4-substituted pyridines, on changing the solvent from benzene to methanol, correlate with the basicity of the solute, which also indicates the importance of hydrogen bonding in determining the solvent dependences of pyridine-nitrogen shifts.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/ja00484a008DOIArticle
http://pubs.acs.org/doi/abs/10.1021/ja00484a008PublisherArticle
Alternate Title:Effects of solvent, protonation, and N-alkylation on the nitrogen-15 chemical shifts of pyridine and related compounds
Additional Information:© 1978 American Chemical Society. Received October 31, 1977. Supported by the Public Health Service, Research Grant GM-11072 from the Division of General Medical Sciences. and by the National Science Foundation
Funders:
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U.S. Public Health Service (USPHS)GM-11072
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Caltech Gates and Crellin Laboratories of Chemistry5696
Issue or Number:16
Record Number:CaltechAUTHORS:20151008-070941921
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20151008-070941921
Official Citation:Effects of solvent, protonation, and N-alkylation on the nitrogen-15 chemical shifts of pyridine and related compounds Rudolf O. Duthaler and John D. Roberts Journal of the American Chemical Society 1978 100 (16), 4969-4973 DOI: 10.1021/ja00484a008
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:60882
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:08 Oct 2015 18:15
Last Modified:03 Oct 2019 09:01

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