Fig. 2: Identifying the tautomer state of a substituted imidazole by 13C NMR spectroscopy.
From: Switching imidazole reactivity by dynamic control of tautomer state in an allosteric foldamer
a, b Computed 13C NMR chemical shifts (using two different functionals, Supplementary Fig. 55) for the two tautomers of methylimidazole (Δδ values shown in ppm). c Model regioisomers 1,4-dimethylimidazole and 1,5-dimethylimidazole. d Experimental 13C NMR chemical shifts (CD2Cl2, 25 °C) for device 1 and benchmark structure 2. The difference in chemical shift (ΔΔδ in ppm) between C4 and C5 is consistently reduced significantly in the tautomer or regioisomer with the protonated or methylated nitrogen adjacent to the C-alkyl substituent.
