Kinetics and mechanism of thermolysis of fluorine substituted 1,2,4-trioxanes in methanol solution

Abstract

The kinetics of the thermal decomposition reactions of two fluorine substituted 1,2,4‐trioxanes: cis‐6‐(4‐fluorophenyl)‐5,6‐{2‐(4‐fluorophenyl)‐propyliden}‐3,3‐tetramethylene‐1,2,4‐trioxacyclohexane (I) and cis‐6‐(4‐fluorophenyl)‐5,6‐{2‐(4‐fluorophenyl)}‐3‐hydroxypropiliden‐3,3‐tetramethylene‐1,2,4‐trioxacyclohexane (II), were investigated in methanol solutions in the temperatures and concentrations ranges of 393.2–428.2 K and (1.05–247) × 10−5 M, respectively. First‐order rate constant values were obtained up to 84–98% conversions of those cyclic peroxides. The corresponding values of the activation parameters for the initial unimolecular homolysis of their molecules, together with the products analyses of the reaction, support stepwise mechanisms of thermolysis. However, similar reaction pathways can be postulated for those reactions but with different ground or transition states for the corresponding peroxidic bond ruptures. Participation of the methanol solvent molecules in secondary free radical reactions of their mechanism is demonstrated. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 523–528, 2000

Solvent and Substituent Effects on the Kinetics of Thermolysis of cis-Fused 1,2,4-Trioxanes

“…The present results parallel those obtained for the thermolysis of substituted 1,2,4,5-tetroxanes which also decompose by unimolecular homolysis of the O-O bond in a stepwise mechanism. Furthermore, the diradical initiated mechanisms of thermolyses in the two solvents investigated, which are also supported by the analysis of the reactions products, are in keeping with those advanced for other cis -fused bicyclic 1,2,4-trioxanes both in the solid state [ 10 ] and in solution [ 11 ].…”

Solvent and Substituent Effects on the Thermolysis of Antimalarial Fluorophenyl Substituted 1,2.4-Trioxanes

“…Herein, the kinetic data on the thermolysis of molecules I and II in methanol solution [ 10 ] is compared with that obtained in n -hexane solution [ 11 ], to examine possible solvent effects in their thermolyses.…”

Synthesis, spectral properties and thermal behaviour of zinc(II) acetylsalicylate

“…The gaseous product was identified qualitatively as CO 2 by bubbling it through limewater [Ca(OH) 2 ] and quantitatively by trapping it in a previously weighed sodalime tube. The organic decomposition products were identified by GC-MS analysis as reported in a previous work [12]. With helium as the carrier gas, samples of the mixture of products dissolved in acetone were injected into a 5890 model, Series II Plus, Hewlett-Packard instrument coupled to a 5972 A model, Hewlett-Packard MSD at 179 • C using an HP 5 MS capillary silica-fused column thermostated at 150 • C with the injector port at 250 • C. The identity of the inorganic product (ZnO) was obtained via wet chemical methods using both qualitative and quantitative tests.…”