DOI: 10.1002/mrc.1409

The tautomerism of Omeprazole in solution: a ¹H and ¹³C NMR study

The tautomerism of 5(6)-methoxy-2-{[(4-methoxy-3,5-dimethyl-2-pyridinyl)methyl] sulfinyl}-1H-benzimidazole (omeprazole) was determined in solution, K_T = 0.59 in THF at 195 K, in favor of the 6-methoxy tautomer. The assignment of the signals was made by comparison with its two N-methyl derivatives in acetone-d₆ and through theoretical calculations of the absolute shieldings (GIAO/DFT/6-311++G**).