1H and13C nuclear magnetic resonance spectra of benzylidenemalononitriles : a method for the determination of σ+substituent constants
- 1 January 1976
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 6,p. 729-732
- https://doi.org/10.1039/p29760000729
Abstract
The 1H and 13C n.m.r. spectra of 15 substituted benzylidenemalononitriles (IIa–o) are reported in detail. The 1H chemical shift of the vinylic hydrogen changes by 0.67 p.p.m. over the range of substituents and may be correlated with either σ or σ+ substituent constants with almost the same degree of confidence (r0.989 for σ and 0.994 for σ+). The 13C chemical shift of the β-vinylic carbon is, however, much more sensitive to substituent effects (range of δ= 17.2 p.p.m.) and shows a clear correlation with the σ+ substituent constants (r 0.996) rather than the corresponding σ values (r 0.968). Three hitherto unreported σ+ values are derived from the data.Keywords
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