✍ Scribed by Cesar Zucco; Evandro L. Dall'Oglio; Gean V. Salmória; Hugo Gallardo; Ademir Neves; Marcos C. Rezende
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A dynamic NMR study of the tautomerism of 2,2'-bisbenzimidazolyl in DMSO-d 6 and a mechanistic interpretation of the process, based on a stepwise, single-proton transfer and formation of a zwitterionic intermediate, are presented. This interpretation is substantiated by semi-empirical calculations of the postulated intermediate and transition state, that yield results which are compared with previous studies on related aliphatic systems.
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## Abstract The ^13^C NMR spectra of several 2‐substituted imidazoles and benzimidazoles have been measured. The substituent was CH~3~, COOH and CONHR, where R = H, __n__‐Bu, __p__‐tolyl or __m__‐chlorophenyl. Carbons 4 and 5 in the imidazoles and the carbon pairs 8/9, 4/7 and 5/6 become equivalent
lSN 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 cu 100 ppm between the iminothiol and thioamide nitrogen atoms, the I5N chemical shifts of t