Chemiluminescence of oxygen-free acetone solutions of dimethyldioxirane

Abstract

The decomposition of dimethyldioxirane (1) in oxygen-free acetone solutions (46 ~ is accompanied by chemiluminescence (CL) in the visible spectral region. The emitter of CL is triplet-excited methyl acetate (2"('I')). For the decomposition of solutions of I in acetone and deuterated dimethyldioxirane in acetone-D 6 the decay of CL follows the first-order kinetics, and the kinetic isotope effect is observed. Two mechanisms of the formation of 2*(T) are discussed: ta) chain-radical process and (b) isomerization of 1 to 2.Key words: organic peroxides, dimethyldioxirane, chemiluminescence, mechanism of chemiluminescence.Formation of excited products in the decomposition accompanied by chemiluminescence (CL) is a general property of several cyclic peroxides. For example, the decomposition of dioxetanes gives ketones in singlet and triplet excited states, i,2 and the decomposition of some ozonides results in the formation of singlet oxygen. 3,4 In the majority of cases, these are precisely the products which are emitters of the luminescence appeared. Cyclic peroxides (dioxiranes 5,6) are not exceptions in this series. The energy released in the decomposition of dioxiranes to the corresponding ester is equal to -80 kcal real -1 al~d, hence, a chemiluminescence process is possible. 5,r In fact, we have shown 8 that the thermal decomposition of dimethyldioxirane (1) in the presence of an activator of CL, 9,10-dibromoanthracene (DBA), results in the appearance of CL caused, as we supposed, by the energy transfer from triplet-excited methyl acetate (2*(T)) (the main product of the decomposition of 1) to DBA. Later, 9 we observed a substantially more intense CL in the decomposition of compound 1 sorbed from the gas phase on the surface of Sitipor. However, zao CL was observed in a solution of i in acetone. We related this fact to the quenching process and, first of all, to the presence of oxygen, an efficient quenching agent of triplet-excited states. In this work, we first report on CL in the thermal decomposition of oxygenfree solutions of 1 in acetone. ExperimentalDioxirane 1 was obtained and analyzed as described in Ref. 10. The kinetics of the decomposition of 1 was monitored spectrophotometrically in a thermostated quartz ceil (the opti-" Dedicated to Prof, W. Adam on the occasion of his 60th birthday.cal path was 1 cm) by the decrease in the optical density at L 335 nm (e 10 L real -I cm-t) t~ on a Specord M-40 instrument (Carl Zeiss, Jena). Chemiluminescence was monitored on an installation of an FEU-140 photomultiplier calibrated in absolute units according to a procedure described previously. It Phosphorescence spectra of methyl acetate (2) were recorded on a Hitachi MPF-4 spectrofluorimeter at 77 K. Oxygen from a solution of 1 in acetone was removed by subsequent "freezing-evacuating-thawing out" procedures repeated 5--6 times until the release of gas bubbles stopped completely. After this, a solution of I in acetone was placed in a therrnostated cell arranged above the photocathode of the photomultiplier, and CL ...

Thermolysis of organic peroxides in solution

“…The first component of Eqn (23) reflects the consumption of compound 7b in the reaction with the acetonyl radical, while the second one describes the contribution of reaction (13) to the total rate of DMDO decomposition. This differential equation is readily transformed into an analytical expression which appears as: 57,66 ln…”

Chemiluminescence occurring upon decomposition of dimethyldioxirane adsorbed from the gas phase onto a silipor surface in the presence of tris(bipyridine)ruthenium(II) and 9,10-diphenylanthracene

“…Thus, it was found that decomposition of dimethyldioxirane (DMD) in an oxygen-free acetone solution was accompanied by light emission. 5 The same phenomenon was observed upon interaction of dioxiranes with tris(bipyridine)ruthenium(II) [Ru(bipy) 3 ] 6 and some aromatic hydrocarbons. 2,7 In addition, dioxirane as intermediate has been postulated as a source of chemiluminescence in a number of chemical 8,9 and biochemical 10 systems.…”

“…ketones: oxygen-free acetone solutions. 5 Obviously, this is associated with the favourable conditions for chemiluminescence on a sorbent surface (for example, the absence of quenching by solvent and different impurities in solution). The other reason obviously lies in the mechanism of DMD decomposition itself.…”

“…The other reason obviously lies in the mechanism of DMD decomposition itself. In fact, in solution (without oxygen) DMD is mainly decomposed by a radical-chain mechanism 5,17 ('dark' reaction). That part of chemiluminescent reaction (1) is negligible.…”

“…That part of chemiluminescent reaction (1) is negligible. 5 Instead, on a sorbent surface the radical-chain processes are not so effective and the isomerization reaction plays a major role in DMD decomposition, which results in a significant increase in chemiluminescence yield.…”