Abstract.
Theoretical studies on the thermolysis in the gas phase of 4-arylideneimino-1,2,4-triazol-3(2H)-ones and 4-arylideneimino-1,2,4-triazol-3(2H)-thiones were carried out using density functional theory methods, at the B3LYP/6-31G(d) and B3LYP/6-311+G(2d,p) levels of theory. The proposed reaction mechanism occurs in one step, leading to the formation of 3-hydroxy-(2H)-1,2,4-triazole or 3-mercapto-(2H)-1,2,4-triazole and a 4-substituted benzonitrile, via a six-membered cyclic transition state. The progress of the reactions was followed by means of the Wiberg bond indices. The results indicate that the transition states have character intermediate between reactants and products, and the calculated synchronicities show that the reactions are slightly asynchronous, in the case of triazolones, and show a higher asynchronicity in the case of triazolthiones. The bond-breaking processes are slightly more advanced than the bond-forming ones, indicating a small bond deficiency in the transition states. Kinetic and activation parameters for the reactions studied have been calculated and compared with available experimental data.
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Acknowledgments.
This work was supported by a research fund provided by the Dirección de Investigaciones Medellín, Universidad Nacional de Colombia, Sede Medellín, and COLCIENCIAS (project no. 1118-05-1148), and the Spanish Dirección General de Investigación, Ministerio de Ciencia y Tecnología (project no. BQU20001499). The authors also thank COLCIENCIAS and C.S.I.C. for the joint project no. 2001CO0004, and the program “Formación de Jóvenes Investigadores” (Ederley Vélez)–COLCIENCIAS.
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From the Proceedings of the 28th Congreso deQuímicos Teóricos de Expresión Latina (QUITEL 2002)
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León, L., Notario, R., Quijano, J. et al. A density functional theory study of the gas-phase elimination reactions of 4-arylideneimino-1,2,4-triazol-3(2H )-ones and their 3(2H )-thione analogues. Theor Chem Acc 110, 387–394 (2003). https://doi.org/10.1007/s00214-003-0492-9
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DOI: https://doi.org/10.1007/s00214-003-0492-9