The carbon-13 chemical shifts and coupling constants of 1168 pyrazoles are reported, some of them in several solvents. These data are briefly discussed on the basis of statistical treatment and qualitative comparisons.
SummaryThis paper reports the 1H, 13C and 15N NMR experimental study of five benzimidazoles in solution and in the solid state (13C and 15N CPMAS NMR) as well as the theoretically calculated (GIAO/DFT) chemical shifts. We have assigned unambiguously the "tautomeric positions" (C3a/C7a, C4/C7 and C5/C6) of NH-benzimidazoles that, in some solvents and in the solid state, appear different (blocked tautomerism). In the case of 1H-benzimidazole itself we have measured the prototropic rate in HMPA-d
18.
Twenty symmetrical and asymmetrical 1,2‐bisazolylethanes have been obtained from azoles and 1,2‐dibromoethane or 1‐chloro‐2‐(pyrazol‐1‐yl)ethane by phase transfer catalysis (PTC). The 1H and 13C nmr properties are reported and the chemical shifts of the ethylene carbon atoms discussed using an additive model.
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