Articulo
A kinetic and mechanistic study on the thermal decomposition reactions of cis- and trans- fused 1,2,4-trioxanes
Autor
Cafferata, Lázaro F. R.
Jeandupeax, Rene
Romanelli, Gustavo Pablo
Mateo, Carmen Margarita
Jefford, Charles W.
Institución
Resumen
The kinetics of the thermal decomposition reactions of artemisinine (1), a cis-fused 1,2,4-trioxane, and trans-3,3dimethyl-1,2,4-trioxane (6) in solutions of benzene, toluene, and methanol in sealed tubes were compared at temperatures between 100.1° and 171.4 °C. Pseudo first-order rate constant values were determined for conversions of both cyclic peroxides up to ca. 60%. The activation parameters and the composition of the reaction products were indicative of homolytic cleavage of their O-O bonds as the rate-determining steps followed by stepwise fragmentation. The free energies of activation (ΔG#) for 1 and 6 reactions in the aromatic solvents were calculated at the middle of each temperature range, giving values of 30.7 and 35.1 kcal/mol, respectively, which are evaluated considering their different molecular configurations. Furthermore, the rates of the thermal decomposition reactions of those trioxanes were sensitive to solvent effects. Laboratorio de Estudio de Compuestos Orgánicos Centro de Investigación y Desarrollo en Ciencias Aplicadas