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1H NMR studies of solvent effects on hydrogen bonding in some pyridine trifluoroacetates

✍ Scribed by Zofia Dega-Szafran; Ewa Dulewicz

Publisher: John Wiley and Sons
Year: 1981
Tongue: English
Weight: 474 KB
Volume: 16
Category: Article
ISSN: 0749-1581
DOI: 10.1002/mrc.1270160310

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✦ Synopsis

Abstract

The chemical shifts of hydrogen bonded protons in complexes of 11 substituted pyridines with trifluoroacetic acid were examined, in five dry solvents of different activity, with respect to proton transfer and aggregation effects. The results were correlated with Δp__K__~a~, the Kirkwood function and E ~T~ parameters. The solvent effect on the intersection point obtained from the plot of the chemical shift of the hydrogen bonded protons against Δp__K__~a~ can be used, similar to an isotopic effect, to differentiate strong hydrogen bonds. The aggregation of acid–base complexes can lead to downfield or upfield shifts; the variation of chemical shift with aggregation depends on the position of the proton in the hydrogen bridge.

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