PMR spectroscopic study of the kinetics of H/D exchange in methyl groups in a series of heterocyclic azines |
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Authors: | M M Markova V P Lezina S B Gashev A U Stepanyantz B V Mislavskii L D Smirnov |
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Institution: | (1) Institute of Chemical Physics, Academy of Sciences of the USSR, Moscow;(2) Scientific-Research Institute of Pharmacology, Academy of Medical Sciences of the USSR, Moscow |
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Abstract: | The rate of H/D exchange among methyl group protons in a series of substituted 3-hydroxypyridines, 5-hydroxypyrimidines, and their N-oxides has been shown to increase with increasing acidity of the medium. The most reactive form of these molecules is the cationic form at pH<2. The rate of H/D exchange of CH3 group protons in 3-hydroxypyridine derivatives has also been found to be several orders of magnitude lower than the rates of exchange for methyl-substituted 5-hydroxypyrimidine and its N-oxide. Effective rate constants for methyl group proton exchange have been estimated. In the case of methyl-substituted 5-hydroxypyrimidine N-oxide derivatives it has been established that the rate of proton exchange is greater for an ortho-methyl group than for a methyl group in the para-position relative to the N-oxide site.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 93–96, January, 1991. |
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