Carbon‐13 NMR studies of olefins having nitrile and methoxycarbonyl substituents. Additivity relationships

Abstract

Carbon-13 NMR chemical shifts are reported for a series of seventeen olefins with tetra-, tri-, di-and mono-snbstitution by nitrile and methoxycarbonyl groups. Analyses of the data for the nitrile, methoxy and carbonyl chemical shifts by mnltiple linear regression provide a good correlation with the pattern of geminal, c h i d and transoid substitution. The olehic shielding data are more complicated, and the analysis requires the introduction of pairwise additivity parameters. It seems likely that the greater complexity arises from steric effects associated with ckoid and geminal methoxycarbonyl substituents, which produce deviations from planarity. The empirical relationships, which are reported here, are useful in removing several ambiguities in the spectral assignments. In this series of compounds it is also observed that substituents which are cis to the nitrile, shift the nitrile resonance 1-2ppm to high field of those for the trans snbstituents.

Donor‐Substituted Cyanoethynylethenes: π‐Conjugation and Band‐Gap Tuning in Strong Charge‐Transfer Chromophores

“…[32] Hall and co-workers investigated the chemical shifts of olefins with CN substituents. [33] An upfield shift was observed for the C atoms of the CN groups with an increasing number of such groups connected to the double bond. This upfield shift is also observed upon going from 3 (1 CN), through 7 (2 CN) and 8 (3 CN), to TCNE (2).…”

Effect of fermentation metabolites on rheological and sensory properties of fermented rice noodles

“…The higher the electron density, the more shielding occurs and an upfield shift will be observed 32. Hall and co‐workers investigated the chemical shifts of olefins with CN substituents 33. An upfield shift was observed for the C atoms of the CN groups with an increasing number of such groups connected to the double bond.…”