Вид документа : Статья из журнала Шифр издания : 54/P 93 Автор(ы) : Khabibulina I.V., Volovodenko A.P. , Trifonov R.E., Yashukova G.V., Mochul`skaya N. N., Charushin V. N., Rusinov G. L., Beresnev D. G., Itsikson N. A., Ostrovskii V.A. Заглавие : Protolytic equilibrium of the isomeric phenyl-1,2,4-triazines [Electronic resource] Место публикации : Chemistry of Heterocyclic Compounds. - 2003. - Vol. 39, № 5. - С. 616-623 Систем. требования: http://www.springerlink.com/content/q87451813175h0j1/fulltext.pdf Примечания : 2.11.2011 г. ББК : 54 Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: The protonation constants for the first and second stages (pK BH+, pKBH2+) of a series of 1,2,4-triazines with a phenyl substituent at various positions in the ring were determined in aqueous solution by a spectrophotometric method. The values of the basicity constants characterizing the first protonation of the heterocycles investigated was in the range of acidity of the medium of pH 3.5 to H0 -2, and the second from H0 -7.3 to H0 -8.7. The position of the phenyl substituent proved to have a significant effect on the size of pK BH+. According to the results of ab initio calculations using HF/6-31G** for the heterocycles investigated the 1H+ form is thermodynamically most stable among the monocations, with the exception of 6-phenyl-1,2,4-triazine for which the existence of the monocation in the 1H+ and 2H+ forms are equally probable. In the case of the dications of all the triazines the 2,4-H,H2+ tautomer is the most preferred. The aromaticity of the 1,2,4-triazine ring is changed insignificantly on mono- and diprotonation. Держатели документа: Центральная научная библиотека УрО РАН Доп.точки доступа: Khabibulina, I.V.; Volovodenko, A.P. ; Trifonov, R.E.; Yashukova, G.V.; Mochul`skaya, N. N.; Charushin, V. N.; Rusinov, G. L.; Русинов Геннадий Леонидович; Beresnev, D. G.; Itsikson, N. A.; Ostrovskii, V.A.