STANDARD GAS-PHASE FORMATION ENTHALPIES AND RELATIVE STABILITY OF С-ALKOXY-1,2,4-TRIAZOLES TAUTOMERIC FORMS AND ISOMERIC N-METHYL-C-METOXY-1,2,4-TRIAZOLES: QUANTUM-CHEMICAL CALCULATIONS
Abstract
The formation enthalpies of tautomeric forms of C-alkoxy-1,2,4-triazoles (alkoxy = OCH3, OC2H5, Oi-C3H7, Ot-C4H9) and isomeric N-methyl-C-methoxy-1,2,4-triazoles have been calculated by means of designed isodesmic and isomerisation reactions. The relative Gibbs energies for their tautomeric forms and isomers in aqueous solution have been calculated. N2-tautomers and isomers of C-alkoxy-1,2,4-triazoles wеre found to have the smallest values of formation enthalpy whereas N4-forms are less stable in gaseous phase. Increasing of electron donor properties of substituent leads to the stabilization of N2-tautomers in comparison with N1-tautomers. N1- and N2-tautomers and isomers have similar values of Gibbs free energy in aqueous solution. In contrast to gaseous phase, N1-derivatives of C-methoxy- and C-ethoxy-1,2,4-triazoles as well as N-methyl-C-methoxy-1,2,4-triazoles are more stable than corresponding N2-derivatives. This is due to higher polarity of N1-isomers in comparison with N2-ones. N4-derivatives are less stable in gaseous phase as well as in aqueous solution.
About the Authors
VADIM E. MATULIS
Научно-исследовательский институт физико-химических проблем, Минск
Belarus
Belarus
Y. I. GRIGORIEV
Научно-исследовательский институт физико-химических проблем, Минск
Belarus
Belarus
G. T. SUKHANOV
Институт проблем химико-энергетических технологий Сибирского отделения РАН, Бийск
Russian Federation
Russian Federation
I. A. KRUPNOVA
Институт проблем химико-энергетических технологий Сибирского отделения РАН, Бийск
Russian Federation
Russian Federation
O. A. IVASHKEVICH
Научно-исследовательский институт физико-химических проблем, Минск
Belarus
Belarus
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