¹⁵N NMR: Iminothiol‐thioamide tautomerism of 2‐mercaptobenzazoles and 1‐methyl‐2‐mercaptoimidazole

Abstract

Abstract 15 N NMR spectra of a number of 2‐mercaptoazoles were obtained and the position of the iminothiol‐thioamide prototropic tautomeric equilibrium was determined. Because of the large chemical shift difference of ca 100 ppm between the iminothiol and thioamide nitrogen atoms, the 15 N chemical shifts of the S ‐methyl and N ‐methyl analogs of each tautomer provided reasonable chemical shift models for the same nitrogen atom in the tautomers. Only a small correction for an N ‐methyl effect was required.