Thermal decomposition of perfluoro-di-t-butyl peroxide

The thermal decomposition of perfluoro-di-t-butyl peroxide has been studied for the first time. The reaction was carried out in the gas phase between 5 and 600 torr in the 108-149°C temperature region. The products consisted solely of C₂F₆ and CF₃COCF₃. The decomposition was found to be first order and homogeneous. The rate constant is given by log k_decomp(sec^?1) = (16.2 ± 1.2) - (148.7 4.4)/2.3RT where R is 0.008314kJ/mol · °K. These Arrhenius parameters are consistent with those determined for the decomposition of di-t-butyl peroxide.     

THE PHOTOCHEMISTRY OF RIBOFLAVIN—V. THE PHOTODEGRADATION OF ISOALLOXAZINES IN ALCOHOLIC SOLVENTS

Abstract— Riboflavin and other N -10 substituted isoalloxazines have been irradiated anaerobically in alcohols and alcohol-water mixtures. Deuterium substitution was used in several different ways to determine the hydrogen kinetic isotope effect. Riboflavin and 10-(3'-hydroxypropyl)-isoalloxazine were photobleached in 2-propanol, 2-propanol-0-d, 2-propanol-2-d, t -butyl alcohol, and t -butyl alcohol-0-d. No isotope effect significantly different from 1.0 was found for any of the nondeuterated to deuterated solvent comparisons. When the anaerobic irradiation of 10-(3'-hydroxypropyl-3',3'-d₂)-isoalloxazine and 10-(3'-hydroxypropyl)-isoalloxazine in either 2-propanol or t-butyl alcohol were compared, kinetic isotope effect ratios for H to D of 2.8 were obtained. Thin layer chromatography in conjunction with color return at 445 nm during oxidation showed that lumichrome and formylmethylflavin, which are irreversible photodegradation products, were formed from the photoreaction in alcohols. The photochemistry of isoalloxazines in alcohols, while somewhat different from the aqueous photochemistry, does not involve a primary photoreduction with the solvent, and photo degradation still dominates. This was an unexpected result and it illustrates the unusual photochemical behavior of isoalloxazines. The anaerobic irradiation of riboflavin in 2-propanol-water mixtures showed that the efficiency of photodegradation is linked to the physical properties of the solvent.