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

The kinetics of the thermal decomposition reactions of two fluorine substit uted 1,2,4-trioxanes: cis-6-(4-fluorophenyl)-5,6-{2-(4-fluorophenyl)-propyl iden)-3,3-tetramethylene- 1,1,2,4-trioxacyclohexane (I) and cis-6-(4-fluoro phenyl)-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 (105-247) x 10 (-5) M, respectively. First-order rate constant values were obtained up to 84-98% conversions of those cyclic peroxides. The corresponding values of t he activation parameters for the initial unimolecular homolysis of their mo lecules, together with the products analyses of the reaction, support stepw ise mechanisms of thermolysis. However, similar reaction pathways can be po stulated for those reactions but with different ground or transition states for the corresponding peroxidic bond ruptures. Participation of the methan ol solvent molecules in secondary free radical reactions of their mechanism is demonstrated. (C) 2000 John Wiley & Sons. Inc.