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An NMR study of hydrogen bonding in some azo dyestuffs |
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| Authors: | J. W. Wiench W. Schilf L. Stefaniak G. A. Webb |
| Affiliation: | a Institute of Organic Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, Warsaw 01-224, 42 POB 58, Poland b Department of Chemistry, University of Surrey, Guildford, GM 2 5XH, UK |
| Abstract: | The 1H, 13C, and 15N NMR data reported for compounds 1–4 show that in DMSO solutions all of them exist in the azo form only and do not participate in the azo–hydrazoimine equilibrium. The NMR data for compounds 1 and 2 show the presence of a weak hydrogen bond for the non-protonated forms, between N10 and the 2-NHCH3 proton. All compounds have also been studied in TFA solutions in which they are protonated. The site of protonation of 1, 2 and 3 is determined to be at N10 in TFA solutions. These results are supported by some ab initio GIAO-CHF molecular orbital calculations. |
| Keywords: | Azo–hydrazimine tautomerism Chemical shift GIAO-CHF molecular orbital calculations |
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