¹⁷O NMR Spectroscopy of Benzoyl Compounds YC₆H₄COX: Sensitivity to Ring Substituents as a Measure of the Electron Demand of the Carbonyl Group

Abstract

ChemInform Abstract (the (mostly) p-Y are not given).

NMR of Terminal Oxygen. Part 13. 17O‐NMR spectra of C‐nitroso compounds, thionitrites and NO+ Ion: Resonance effects in ON—X compounds and correlation with CD spectra

“…These are indications that the bond-order term of Eqn. I influences the shielding, though the correlation is less strict than in the case of the CO compounds RCOX [5]. On the other hand, it is evident from Fig.…”

“…10 kcal/mol[3]; measurements of dipole moments and bond lengths confirm the existence of resonance-type interactions in N-nitrosamines [4]. In other functional groups, however, the resonance interaction of a potential n-donor with NO is less well established.We have shown that, in contrast to I3C-, "0-NMR spectroscopy is particularly useful to establish the presence of resonance interaction of CO groups with n-donors [5]. If the donor atom belongs to the second row of the periodic table (C, N, 0, F), the shift values indicate the electrophilicity of the CO group and, indirectly, the degree of intervention of the n-donor: in the absence of donors, as in aldehydes and ketones, the shift value 6(I7O) is ca.…”

“…If the donor atom belongs to the second row of the periodic table (C, N, 0, F), the shift values indicate the electrophilicity of the CO group and, indirectly, the degree of intervention of the n-donor: in the absence of donors, as in aldehydes and ketones, the shift value 6(I7O) is ca. 550 ppm [6], whereas n-donors cause an upfield shift, as in COOR (330 ppm), CONR, (320 pprn), COC-R, (325 ppm) [7], and COO-(265 ppm) [5]. Third-row atoms, …”

“…As in the series of carbonyl compounds, conjugation with S (in mercapto-esters [5] [15]) shows only a slight effect on 6(I7O), we included measurements of S-nitroso compounds (thionitrites). Finally, we measured NO'BF;, in order to include the nitrosyl ion lacking an attached group X.…”

“…1,4-naphthoquinone, 572 ppm [20]; the strong H-bridge between =NOH and =O would be expected to increase the shielding of the latter [21]. The oxime groups of 5B and 6B manifest themselves by signals at 229 ppm (5) and 265 ppm (6); we found for acetone oxime (7) a signal at 177 ppm, other oximes have been found at 170-195 ppm [22]. The difference between the 1-oxime 5B and the 2-oxime 6B can be attributed to differences in chelation (1 > 2), manifest also in solubility and in IR spectra [19].…”