A Study of Hindered Internal Rotation in Some N-Vinyl-Substituted Amides by Nuclear Magnetic Resonance Spectroscopy¹

N‐Alkenyl amide rotational barriers by 2D EXSY NMR

“…Although an enormous amount of literature is available on the study of amide rotational barriers, 12,14,15 there is very little information on barriers where the amide nitrogen is in conjugation with a carbon-carbon double bond. Only one reference, to a study of acyclic N-vinylamides, 16 was found in the NMR studies reported on amide bond rotation in solution. 12,14 -16 The 2D EXSY NMR technique has been widely used to measure quantitative kinetic data and to gain mechanistic insight into rotational barriers in simple organic and organometallic compounds.…”

“…The trend in the G 6 D values suggests that conjugation of the nitrogen lone pair with the N-styryl group decreases the amide rotational barrier by as much as 2.6 kJ mol 1 relative to the saturated N-alkyl-substituted amide 2. 16 The relatively low barrier to rotation in 3 probably arises mainly from a steric interaction between the phenyl ring and the amide carbonyl oxygen. This indicates that the secondary N-alkenylamides studied here have significantly less steric requirement than formanilide (3).…”

Viscosity monitoring study of the kinetics of aqueous‐medium N‐vinylpyrrolidone free‐radical polymerization

“…Stach et al . and Gehring et al . have concluded that the π bond tends to compete with the carbonyl group for the lone pair electrons in the nitrogen atom.…”

N-Vinylformamide — Syntheses and Chemistry of a Multifunctional Monomer

“…Further investigations of Gehring et al [54], Ajo et al [55] (ab initio and PEM calculations) and Yoder and Gardner [56] show that the barriers to rotation of the partial C=N double bond are lowered by the vinyl group compared with saturated alkyl groups. This indicates that the vinyl group competes with the electronegative oxygen for the lone pair on the nitrogen and thus reduces the double bond character of the C=N bond.…”

“…Deprotonation follows the electrophilic addition of a trifluoroacetyl cation even under the reaction conditions at 54 room temperature, whereby regiospecific trans-β-substitution takes place with formation of N-(β-trifluoroacetylvinyl)pyrrolidone 56 (28).…”