Tautomeric behaviour and isotopic multiplets in the C-13 NMR spectra 5-arylazo-pyrimidine (of partially deuterated 1H,3H,5H)-2,4,6-triones and 5-arylazo-2-thioxo-pyrimidine (1H,3H,5H)-4,6-diones - evidence for elucidation of tautomeric forms

摘要

NMR spectra of the synthesized azo dyes, 5-arylazo-pyrimidine (1H,3H,5H)-2,4,6-triones (5a-g), 1,3-dimethyl-5-arylazopyrimidine (1H,3H,5H)-2,4,6-triones (6a-g), and 5-arylazo-2-thioxo-pyrimidine (1H,3H,5H)-4,6-diones (7a-g) were studied in (CD3)(2)SO(three drops of CD3OD were added into solutions of the dyes in two different concentrations). All dyes showed intramolecular hydrogen bonding. Dyes 5a-7a showed bifurcated intramolecular hydrogen bonds. Tautomeric behaviours of some of N-methylated azo dyes (6a-g) were studied in two different concentrations. The solvent-substrate proton exchange of dyes 5a-d, 6a and 7a-e was examined in presence of three drops of CD3OD. The dyes which were soluble in (CD3)2SO containing CD3OD showed isotopic splitting (beta-isotope effect) in the C-13 NMR spectra. Copyright