13C NMR spectra of non-labelled and 15N-mono-labelled azo dyes |
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Authors: | Antonín Ly
ka Dobroslav nobl Vladimír Mach
ek Miroslav Ve
ea |
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Institution: | Antonín Ly?ka,Dobroslav ?nobl,Vladimír Machá?ek,Miroslav Ve?e?a |
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Abstract: | 13C NMR spectra of four types of azo coupling products from benzenediazonium chloride have been measured and interpreted, viz. hydrazo compounds with an intramolecular hydrogen bond (3-methyl-1-phenylpyrazole-4,5-dione 4-phenylhydrazone), azo compounds without an intramolecular hydrogen bond (4-hydroxyazobenzene), azo compounds with an intramolecular hydrogen bond (2-hydroxy-5-tert-butylazobenzene) and an equilibrium mixture of both the tautomers of 1-phenylazo-2-naphthol. The absolute values of the J(15N13C) coupling constants have been determined by recording the spectra of the 15N isotopomers, and have been used, in some cases, for 13C signal assignment. A relationship has been found between the chemical shifts of the C-1′ to C-4′ carbons of the phenyl group (from the benzenediazonium ion) or the 1J(15N13C) coupling constant, and the composition of the tautomeric mixture. |
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