Transmission of substituent effects through unsaturated systems. I—relative magnitudes of proton and carbon substituent chemical shifts in ethylenes, butadienes, α-enones and benzenes
✍ Scribed by Marcel Azzaro; Jean-François Gal; Serge Géribaldi; Nicole Novo-Kremer
- Publisher
- John Wiley and Sons
- Year
- 1977
- Tongue
- English
- Weight
- 393 KB
- Volume
- 9
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
Abstract
The carbon‐13 shifts of C‐1, C‐2 and C‐3 are determined in a series of 1‐cyclohexen‐3‐ones substituted in position 1. Linear relationships are demonstrated between the substituent chemical shifts of corresponding carbons in substituted ethylenes, butadienes, α‐enones and benzenes. The substituent chemical shifts of proton H‐2 are also reported and correlated with those of corresponding protons in ethylenes and benzenes. The slopes of the lines for the carbons directly linked to the substituent are close to unity, showing a relative independence of the substituent effect for this nucleus from the variation of the unsaturated framework. In contrast to this, the transmission of the substituent effect through one double bond (nuclei β to the substituents) decreases as the number of conjugated π bonds in the whole structure increases. This relationship is interpreted as being due to the ability of an unsaturated system to spread the variation of π electron density induced by the substituent.