The stability of benzoyl peroxide by isothermal microcalorimetry
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Isothermal microcalorimetry
Peroxide
Isothermal process
Spectrophotometry
Organic peroxide
Benzoyl peroxide is commonly used in the treatment of acne, even though some adverse effects have been reported, probably mediated by the formation of peroxide-derived free radicals and the depletion of antioxidants. In the present work we have studied, in a chemical system, the effect of alpha-tocopherol on benzoyl peroxide radical decomposition to analyse the presence of an interaction between these two compounds, leading to an enhanced peroxide-cytotoxicity, as we have previously reported. Under our experimental conditions alpha-tocopherol strongly amplified the peroxide free radical decomposition occurring either in the presence or in the absence of UV irradiation, and lead to the formation of an unknown radical species in addition to benzoyloxy, phenyl and tocopheroxyl free radicals. The results of this study show that the enhancement of benzoyl peroxide toxicity in cells exposed simultaneously to this peroxide and alpha-tocopherol, is likely due to the generation of the detected radical species.
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The photopolymerization of vinyl acetate has been found to be very much accelerated by the presence of small quantities of benzoyl peroxide. This is considered to be the result of a photochemical decomposition of the peroxide, to give free radicals such as phenyl and benzoate. The dependence of the rate of polymerization on the peroxide concentration suggests that there is a considerable inhibition of the reaction due to the presence of the peroxide. The value of the intensity exponent approaches unity as the concentration of the peroxide is increased, and the formal analysis of the reaction suggests that the inhibition is due to the peroxide molecules themselves. The analysis of the induction period and the dark period shows that these are identical and therefore real, so that it can be concluded that they depend essentially on the nature of the initiation step. The value of the initiation velocity coefficient is calculated, and the energy of activation for this step is found to be 8.4 kcal./g.mol.
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Vinyl acetate
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Cross compounds in polyethylenes occur from the effect of benzoyl peroxide in the same manner as by ionizing radiation or uv light, through the recombination of polymer radicals. The compounds between the macromolecules represent the resultant of a chain process of the decomposition of benzoyl peroxide in polyethylenes. The quantitative expression of the velocity of the appearance of cross compounds depends on the analysis of the interaction velocity of the polymer radicals on the basis of the kinetic constants of the peroxide decomposition and the transfer of the primary radicai to the polymer. (tr-auth)
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Abstract In Propiophenon zersetzen sich die Peroxide (Ib) ausschließlich durch spontane Homolyse der O‐O‐Bindung, das Peroxid (Ia) sowohl spontan wie radikalinduziert, und das Peroxid (Ic) spontan und autokatalytisch.
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Benzoyl peroxide labelled with carbon-14 has been used to sensitize the polymerization of styrene at 60°C. Experiments have been performed with bulk styrene and with various solutions of styrene in benzene. The rate of initiation by benzoyloxy radicals has been measured by using peroxide labelled in the carboxyl groups only; the total rate of initiation, by phenyl as well as by benzoyloxy radicals, has been measured by using peroxide labelled in the benzene rings only. It has been shown that the fraction of the initiating radicals which are benzoyloxy radicals decreases as the concentration of monomer is reduced; it is possible to compare the velocity constants for the alternative reactions of the benzoyloxy radicals, namely, loss of carbon dioxide to give phenyl radicals and capture by molecules of styrene.
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Characteristic features of the polymerization of methyl methacrylate in the presence of ferrocene and various material initiators: benzoyl peroxide, bis( t -butylcyclohexyl)peroxydicarbonate, lauryl peroxide and azo-izo-butyric dinitrile were investigated. It is shown that the introduction of ferrocene in the initiating system affects both the rate of polymerization and on the form of the kinetic curves not only when used as the initiator, benzoyl peroxide, as stated earlier, but also when using other peroxide initiators and peroxide type. In this case, ferrocene can have an accelerating effect on the decomposition of peroxide or participate in the formation of focal active centers.
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H. B. Henbest, J. A. W. Reid and C. J. M. Stirling, J. Chem. Soc., 1964, 1217 DOI: 10.1039/JR9640001217
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Diphenyl ether
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Abstract The vulcanization of natural rubber by benzoyl peroxide between 110° and 50° C has been investigated. The analysis of the kinetics has led to the following results: 1. The benzoyl peroxide concentration decreases at all temperatures according to a reaction of the first order. The velocity constants have been given. 2. Benzoic acid is formed in a slower reaction, but also according to a first order rate. The limiting value of benzoic acid formation depends on the temperature. It decreases with increasing temperature. The velocity constants for benzoic acid formation have been calculated. 3. With larger additions of peroxide to the rubber, both reactions are of the zero order as long as the solubility limit of the peroxide is exceeded. 4. The temperature dependence of the velocity constants of both reactions has been discussed, and it has been shown that at lower temperatures the formation of benzoic acid and the decrease of peroxide become equally rapid. 5. The analogy between thiuram vulcanization and peroxide vulcanization with respect to their kinetics has been pointed out. 6. It has been made apparent that, in both peroxide vulcanization and thiuram vulcanization, one is obliged to assume the formation of an intermediate compound. But, at the same time, it is not possible to make this consistent with the reaction mechanism which Farmer has developed for peroxide vulcanization, nor to apply to peroxide vulcanization the relationships found by Bartlett for the polymerization of allyl acetate by benzoyl peroxide.
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