Protonation of 1,2,4-triazine 4-oxides |
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Authors: | R. E. Trifonov V. A. Ostrovskii V. L. Rusinov O. N. Chupakhin |
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Affiliation: | 1277. St. Petersburg State Institute of Technology, Moskovskii pr. 26, St. Petersburg, 190013, Russia 2277. St. Petersburg State University, Universitetskii pr. 26, St. Petersburg, 198504, Russia 3277. Institute of Organic Synthesis, Ural Branch, Russian Academy of Sciences, ul. Akademicheskaya/S. Kovalevskoi 22/20, Yekaterinburg, 620990, Russia
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Abstract: | The basicity of some 1,2,4-triazine 4-oxides was estimated on a quantitative level, and their probable protonation patterns were ascertained. The dissociation constants of mono- and diprotonated 3-R-6-phenyl-1,2,4-triazine 4-oxides in aqueous buffer solutions and aqueous sulfuric acid solutions were determined (6-phenyl-1,2,4-triazine 4-oxide: $pK_{BH^ + } = 1.1$ , $pK_{BH^{2 + } } = - 6.02$ ). According to the results of DFT calculations (B3LYP/6-311**) and spectral data, first protonation of 1,2,4-triazine 4-oxides involves the N1 nitrogen atom, and the second proton adds to the N-oxide oxygen atom. |
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