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In the (1)H and (13)C NMR spectra of 1-(2-selenophenyl)-1-alkanone oximes, the (1)H, the (13)C-3 and (13)C-5 signals of the selenophene ring are shifted by 0.1-0.4, 2.5-3.0 and 5.5-6.0 ppm, respectively, to higher frequencies, whereas those of the (13)C-1, (13)C-2 and (13)C-4 carbons are shifted by 4-5, approximately 11 and approximately 1.7 ppm to lower frequencies on going from the E to Z isomer. The (15)N chemical shift of the oximic nitrogen is larger by 13-16 ppm in the E isomer relative to the Z isomer. An extraordinarily large difference (above 90 ppm) between the (77)Se resonance positions is revealed in the studied oxime isomers, the (77)Se peak being shifted to higher frequencies in the Z isomer. The trends in the changes of the measured chemical shifts are well reproduced by the GIAO calculations of the (1)H, (13)C, (15)N and (77)Se shielding constants in the energy-favorable conformation with the syn orientation of the-C=N-O-H group relative to the selenophene ring.

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The (1)H, (13)C and (15)N NMR studies have shown that the E and Z isomers of pyrrole-2-carbaldehyde oxime adopt preferable conformation with the syn orientation of the oxime group with respect to the pyrrole ring. The syn conformation of E and Z isomers of pyrrole-2-carbaldehyde oxime is stabilized by the N-H...N and N-H...O intramolecular hydrogen bonds, respectively. The N-H...N hydrogen bond in the E isomer causes the high-frequency shift of the bridge proton signal by about 1 ppm and increase the (1)J(N, H) coupling by approximately 3 Hz. The bridge proton shows further deshielding and higher increase of the (1)J(N, H) coupling constant due to the strengthening of the N-H...O hydrogen bond in the Z isomer. The MP2 calculations indicate that the syn conformation of E and Z isomers is by approximately 3.5 kcal/mol energetically less favorable than the anti conformation. The calculations of (1)H shielding and (1)J(N, H) coupling in the syn and anti conformations allow the contribution to these constants from the N-H...N and N-H...O hydrogen bondings to be estimated. The NBO analysis suggests that the N-H...N hydrogen bond in the E isomer is a pure electrostatic interaction while the charge transfer from the oxygen lone pair to the antibonding orbital of the N-H bond through the N-H...O hydrogen bond occurs in the Z isomer.

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In the acetylenic aldehyde oximes with substituents containing silicon and germanium, the (13)C NMR signal of the C-2 carbon of triple bond is shifted by 3.5 ppm to lower frequency and that of the C-3 carbon is moved by 7 ppm to higher frequency on going from E to Z isomer. A greater low-frequency effect of 5.5 ppm on the C-2 carbon signal and a greater high-frequency effect of 11 ppm on the C-3 carbon signal are observed in the analogous acetylenic ketone oximes. The carbon chemical shift of the C=N bond is larger by 4 ppm in E isomer relative to Z isomer for the aldehyde and ketone oximes. The (29)Si chemical shifts in the silicon containing acetylenic aldehyde and ketone oximes are almost the same for the diverse isomers. The trends in changes of the measured chemical shifts are well reproduced by the gauge-including atomic orbital (GIAO) calculations of the (13)C and (29)Si shielding constants.