Spectroscopic effects and intramolecular interactions in the1H and13C NMR spectra of five-membered N-vinyllactams

In 1-vinylpyrrolidone, 1-vinyl-1,2,4-triazole-5-ones, 1,3-divinylimidazolidine-2-thione, and 1-vinylbenzimidazole-1-thione the vinyl groups exist predominantly in the s-trans-, but in 1-vinyl-4,5-diphenylimidazole-2-ones in the s-cis(0)-conformations relative to the exocyclic heteroatom. In 1-vinylbenzimidazole-2-ones, 3-vinylbenzoxazole-2-one, and 1-vinylindole-2,3-diones the vinyl group is present as a mixture of the s-cis(0)- and s-trans(0)-conformations. According to¹H and¹³C NMR results there are specific intramolecular interactions in 1-vinylpyrrolidone and in 1,3-divinylimidazolidine-2-thione resembling weak hydrogen bonding between the -hydrogen atoms of the vinyl group and the oxygen or the sulfur atom. In 1-vinylsuccinimide, 2-vinylphthalimide, and 1,3-divinyl-4,5-diphenylimidazole-2-one there is the same type of interaction with the -cis-hydrogen atom of the vinyl group, while in 1,3-divinyl-1,2,4-triazole-5-one there is interaction between the same hydrogen atom and the nitrogen atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1983–1990, September, 1990.