4-Carboxyl-2, 6-dinitrophenylazohydroxynaphthalenes tautomerism NMR re-explained and other methods verified. (July 2017)

• Record Type: Journal Article
• Authors: Hristova, Silvia; Angelova, Silvia; Hansen, Poul Erik; Antonov, Liudmil
• Is Part Of: Dyes and pigments. Volume 142(2017)
• Page Start: 226
• Page End: 229
• Publication Date: 2017-07
• Subjects: 1-((2-nitrophenyl)diazenyl)naphthalen-2-ol -- Tautomerism -- Quantum chemistry -- DFT -- UV–Vis spectroscopy -- NMR; Dyes and dyeing -- Periodicals; Pigments -- Periodicals; 667.2
• DOI: 10.1016/j.dyepig.2017.03.037
• Languages: English
• ISSNs: 0143-7208

Abstract

Abstract: In two consecutive studies the tautomerism in 4-((2-hydroxynaphthalen-1-yl)diazenyl)-3, 5-dinitrobenzoic acid and the structurally similar 1-((2-nitrophenyl)diazenyl)naphthalen-2-ol has been considered from viewpoint of theoretical chemistry, UV–Vis spectroscopy and NMR. Although the theoretical data (at M062X level) show that both compounds exist only as a keto tautomer, the experiment proves existence of the enol form. The difference in the results obtained by UV–Vis spectroscopy and NMR requires a deeper consideration and verification of the NMR approach, which is based on using model compounds to provide the NMR signal pattern of individual tautomers. Graphical abstract: Highlights: The NMR approach for tautomerism analysis in 1-((2-nitrophenyl)diazenyl)naphthalen-2-ol is verified theoretically. There is no concentration effect on the tautomerism in the studied compounds in DMSO. In spite of the different approaches used, results from NMR and UV–Vis spectroscopy are in reasonable agreement.