Studies of nuclear magnetic resonance chemical shifts caused by protonation. Part I. Substituted acetamides and some N-methyl- and NN-dimethyl-derivatives
- 1 January 1969
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society B: Physical Organic
- p. 385-389
- https://doi.org/10.1039/j29690000385
Abstract
Chemical shifts caused by protonation of ten substituted acetamides and seven of their N-methyl- and NN-dimethyl-derivatives have been studied in sulphuric acid solutions at 33·5° and 60 MHz, relative to t-butylammonium ion as internal reference. The protons of the aliphatic radicals and of the N-methyl groups all undergo downfield chemical shifts with increasing acidity. These shifts follow a sigmoid dependence on the acidity function HA, from which apparent pKBH+ values for amides have been obtained. These are linearly related to the pKa values of the corresponding carboxylic acids.Keywords
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