Thermal decomposition of p-methyl-p'-nitrobenzoyl and bis-p-nitrobenzoyl peroxides

Differential enthalpic analysis was carried out below the melting point as well as at regular increases of temperature over the melting point of peroxides. From these measurements it follows that the thermal stabilities of peroxides in the solid state increase with their melting points. The rise in the melting point of the peroxide due to changed chemical structure is accompanied by a rise in the melting points of products which in turn affects the isothermal autocatalytic decomposition. The common feature of the thermal decomposition of the peroxides studied below their melting points is a very high apparent activation energy of the initiation of a chain decomposition reaction which is several times higher than that of a spontaneous thermal decomposition of peroxide in solution or in a melt of peroxide. p]From the study of the decomposition of nitro derivatives of benzoyl peroxide in solution it is known¹ that the electron attracting nitro-substituents have a retarding effect on the spontaneous decomposition of peroxides. The introduction which accompanies its thermal decomposition in solution². However not only the substitution of nitro groups in the molecule but also the presence of nitro compounds accelerates the decomposition of benzoyl peroxide³. This indicates that the decomposition reaction may be influenced not only by an intramolecular rearrangement of electrons but also by an intermolecular interaction of nitro compounds with the peroxidic compounds or radicals generated by them. The substitution of methyl groups for hydrogen in aromatic rings does not produce any marked changes in the decomposition reactions of benzoyl peroxide². p]Among other changes produced by substitution, the physical changes—in particular, the changes in the melting points of investigated substances—are of importance to out study of the thermal decomposition of nitro derivatives of nitro derivatives of benzoyl peroxide. These data are interesting mainly because the decomposition of peroxides is influenced by the state of aggregation of the decomposing substances.     

Addition of radicals to quinones—I. ESR study of addition products from chloroquinones and free radicals

The mechanism of addition reactions of radicals formed during thermal decomposition of benzoyl peroxide with various chloro-substituted p-benzoquinones has been studied by the ESR technique in various solvents. The ESR spectra of the intermediate radicals show that addition occurs at the carbonyl oxygen. The important role of charge-transfer complexes in the reaction has been established. For strong CT complexes, the quinone molecule reacts with radicals derived from the solvent.     

Grafting of maleic anhydride on polyethylene. I. Mechanism of grafting in a heterogeneous medium in the presence of radical initiators

Polyethylene has been grafted with maleic anhydride, as proved by the infrared spectra and the properties of the grafted films. The influence of oxygen and a comparison of the effectiveness of benzoyl peroxide and AIBN showed that polyethylene macroradicals are formed through the decomposition of hydroperoxide and peroxide groups. Side chains of poly(maleic anhydride) are formed by a combination of polyethylene macroradicals with those of poly(maleic anhydride). This mechanism of reaction was confirmed by the influence of the amount of film, the initiator and monomer concentrations, and temperature on the percentage of grafting.     

A novel capillary microliter droplet sample injection-chemiluminescence detector and its application to the determination of benzoyl peroxide in wheat flour

A novel capillary microliter order droplet injection-chemiluminescence (CL) system is proposed. In this system, the liquid sample microdrops, automatically formed at the end of a capillary tip by the effect of the gravity and the gas pressure, repeatedly drop into the miniature reaction cell and reacts with CL reagent to generate CL signal. The phenomena of sample zone dilution and spreading are eliminated as the capillary is used as the sample channel and gas pressure is used as driving force without the liquid carrier stream. Therefore, a high sensitivity is obtained. To evaluate the applicability of the proposed method, a determination of benzoyl peroxide (BP) is examined. The system shows that the benzoyl peroxide is detected linearly in the concentration range from 5×10⁻¹⁰ to 1×10⁻⁶ g ml⁻¹. The detection limit (signal-to-noise ratio=3) is 1.4×10⁻¹⁰ g ml⁻¹ for benzoyl peroxide (mass concentration is 1.1 pg, i.e., 4.5 fmol), which is the best result reported so far. The relative standard deviation (n=11) is 1.5% for 2.0×10⁻⁸ g ml⁻¹ BP. The proposed detector for the detection of benzoyl peroxide offers the advantages of sensitivity, simplicity, rapidity, automation and miniaturization. The proposed method has been applied satisfactorily to the determination of benzoyl peroxide in wheat flour.     

Radical reactions in the photodeccomposition of benzoyl peroxide in solid polycarbonate

Conclusions The decomposition of benzoyl peroxide in solid polycarbonate under UV irradiation is a monomolecular chain process.This process is accompanied by the intensive formation of colored products. After complete decomposition of the benzoyl peroxide, this process passes over to a new initiator stage for continued photoreaction of the polycarbonate. A reaction scheme is proposed which involves chain radical reactions, some with participation of polycarbonate macroradicals.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 66–74, January, 1977.     

Singlet oxygen production in the reaction of superoxide with organic peroxides

[reaction: see text] A selective chemiluminescent probe for singlet oxygen has been employed to detect and quantify singlet oxygen in the reactions of superoxide with organic peroxides. The production of singlet oxygen has been quantified in the reaction of superoxide with benzoyl peroxide (BP). No singlet oxygen was detected in the reactions of superoxide with cumyl peroxide, tert-butyl peroxide, or tert-butyl hydroperoxide. On the basis of these results and on the temperature dependence of the reaction, we proposed a mechanism for singlet oxygen formation in the reaction of superoxide with BP.     

Theoretical Studies on Thermal Decomposition of Benzoyl Peroxide in Ground State

Systematic studies of the thermal decomposition mechanism of benzoyl peroxide(BPO) in ground state,leading to various intermediates, products and the potential energy surface(PES) of possible dissociation reactions were made computationally. The structures of the transition states and the activation energies for all the paths causing the formation of the reaction products mentioned above were calculated by the AM1 semiempirical method. This method is shown to to be one predict correctly the preferred pathway for the title reaction. It has been found that in ground state, the thermal decomposition of benzoyl peroxide has two kinds of paths. The first pathway PhC(O)O--OC(O)Ph→PhC(O)O→Ph CO2 produces finally phenyl radicals and carbon dioxide. And the second pathway PhC (O) OO--C (O) Ph→PhC (O) OO PhC (O)→PhC(O) O2→Ph CO O2, via which the reaction takes place only in two steps, produces oxygen and PhC(O) radicals, and the further thermal dissociation of PhC(O) is quite difficult because of the high activation energy in ground state. The calculated activation energies and reaction enthalpies are in good agreement with the experimental values. The research results also show that also the thermal dissociation process of the two bonds or the three bonds for the benzoyl peroxide doesn‘t take place in ground state.     

Décomposition du peroxyde de benzoyle dans les mélanges benzéne/X-4 pyridines (X = CH3, H,CN). etude cinétique et influence des substituants sur la réactivité nucléophile et radicalaire de l'atome d'azote

Effect of a 4-substituent in the pyridine ring upon the decomposition kinetics of benzoyl peroxide in 4-X pyridine/benzene binary mixtures(X = CH₃,H,CN) has been studied. The second-order rate constant for the pyridine-induced decomposition was 2xl0^-6l mol^-1 s^-1 and in 4-methylpyridine it was l0^-5 l mol^-1 s^-1, a five-fold increase, whereas there was no nucleophilic attack on the peroxide oxygen atoms of benzoyl peroxide by 4-cyanopyridine. The surprisingly high increase of the radical-induced decomposition in 4- cyanopyridine might result from the attack at the nitrogen atom of the pyridine ring by the phenyl radical, the 1-phenylpyridinyl radical being stabilized by the cyano group.     

Polymerization of cyclic ethers in the presence of maleic anhydride. Part II. Investigation of the polymerization mechanism

In order to elucidate the reaction mechanism of both the radiation-induced and benzoyl peroxide-catalyzed polymerizations of cyclic ethers in the presence of maleic anhydride, the development of color during reaction and copolymerization of oxetane derivatives were investigated. Upon addition of a small amount of the γ-ray or ultraviolet-irradiated equimolar solution of a cyclic ether and maleic anhydride to isobutyl vinyl ether, a rapid polymerization took place, and the resulting polymer was confirmed to be a homopolymer of isobutyl vinyl ether. A heated solution of dioxane, maleic anhydride, and a small amount of benzoyl peroxide can initiate the polymerization of isobutyl vinyl ether in the same manner. The electrical conductivity of a 1:1 mixture of maleic anhydride and dioxane is increased by about a factor of ten after ultraviolet irradiation. These results indicate that some cationic species are actually formed in the system by irradiation or the decomposition of added benzoyl peroxide. The mechanism of formation of the cationic species responsible for the initiation may be explained as follows. A free radical of an ether is formed by abstraction of a hydrogen atom attached to the carbon adjacent to oxygen atom, followed by a one-electron transfer from the resulting radical to maleic anhydride, an electron acceptor, to yield the cationic species of the ether and the anion-radical of maleic anhydride, respectively. The resulting cationic species as well as the counteranion-radical are resonance-stabilized. Therefore, the present polymerization may be designated a radical-induced cationic polymerization.     

过氧化苯甲酰的热分解研究

The thermal decomposition process of benzoyl peroxide was investigated by Accelerating Rate Calorimeter. The curves of thermal decomposition temperature and pressure versus time for the systems were obtained. The curves of temperature rising-rate versus thermal decomposition temperature were also obtained. After the data revision disposal and analysis processing, thermal decomposition parameters and kinetic data of benzoyl peroxide were calculated, respectively.     

Decomposition of diacyl peroxides in HMPA — An electron transfer process

In hexamethylphosphoric triamide (HMPA), four representative diacyl peroxides, namely, benzoyl peroxide (1), Cyclopropylformyl peroxide (2), lauroyl peroxide (3) and trifluoroacetyl peroxide (4), all decompose at rates much higher than those expected from their unimolecular thermal decomposition, and the corresponding carboxylic acids are formed in high yields (74–97%). Furthermore, several radical colligation products formed from HMPA molecules can be identified. Evidently, the initial step in the reaction between a diacyl peroxide and the “solvent” HMPA involves an electron transfer with the latter acting as the donor.     

Efficiency of Electron Transfer Initiated Chemiluminescence

Although the mechanisms of many chemiluminescence (CL) reactions have been intensively studied, no general model has been suggested to rationalize the efficiency of these transformations. To contribute to this task, we report here quantum yields for some well‐characterized CL reactions, concentrating on recent reports of efficient transformations. Initially, a short review on the most important general CL mechanisms is given, including unimolecular peroxide decomposition, electrogenerated CL, as well as the intermolecular and intramolecular catalyzed decomposition of peroxides. Thereafter, quantum yield values for several CL transformations are compiled, including the unimolecular decomposition of 1,2‐dioxetanes and 1,2‐dioxetanones, the catalyzed decomposition of appropriate peroxides and the induced decomposition of properly substituted 1,2‐dioxetane derivatives. Finally, some representative examples of quantum yields for complex CL transformations, like luminol oxidation and the peroxyoxalate reaction, in different experimental conditions are given. This quantum yield compilation indicates that CL transformations involving electron transfer steps can occur with high efficiency in general only if the electron transfer is of intramolecular nature, with the intermolecular processes being commonly inefficient. A notable exception to this general rule is the peroxyoxalate reaction which, also constituting an example of an intermolecular electron transfer system, possesses very high quantum yields.     

Grafting in reaction of polyethylene and poly(maleic anhydride)

Polyethylene has been grafted in a reaction with poly(maleic anhydride) in the presence of radical initiators. The role of oxygen, the comparison of the effectiveness of benzoyl peroxide and AIBN, and the kinetics of the reaction suggest that side chains are formed via a combination of the macroradicals of both polymers.     

过氧化苯甲酰的安全性研究

利用分子结构特性对过氧化苯甲酰的分解原理进行了分析,并通过热分析、撞击感度和爆发点试验对其安全性进行了评价,得到相关的安全数据。     

Singlet oxygen generated from the decomposition of peroxymonocarbonate and its observation with chemiluminescence method

The decomposition of peroxymonocarbonate (HCO(4)(-)) has been investigated by flow-injection chemiluminescence (CL) method. An ultraweak CL was observed during mixing the bicarbonate and hydrogen peroxide solution in organic cosolvent. An appropriate amount of fluorescent organic compounds, such as dichlorofluorescein (DCF), was added to the HCO(4)(-) solution, a strong CL was recorded. Based on studies of the spectrum of fluorescence, CL and UV-vis spectra, electron spin trapping (ESR) technique, mass spectra (MS) and comparison with H(2)O(2)/hypochlorite (ClO(-)) and H(2)O(2)/molybdate (MoO(4)(-)) systems, the CL mechanism was proposed. The reaction is initiated by unimolecular homolysis of the peroxo O-O bond in HO-OCOO(-) molecule. It was suggested that the bond rearrangement within radicals yield superoxide ion (O(2)(*-)). The interaction of superoxide ion with perhydroxyl radical produces singlet oxygen ((1)O(2)). The energy transfers from singlet oxygen to DCF forming an excited energy acceptor (DCF*). Luminescence (lambda(max)=509 nm) was emitted during the relaxation of the energy acceptor to the ground state.     

The interaction between polymerization initiators and inhibitors in solutions—II. The reaction between benzoyl peroxide and p-benzoquinone in concentrated solutions; Some observations on the induced decomposition of the peroxide

The reaction between benzoyl peroxide and p-benzoquinone in concentrated solutions in a wide variety of solvents has been investigated by isolation and identification of the reaction products. Despite the high efficiency of p-benzoquinone as a trap for benzoyloxy radicals, partial decarboxylation to phenyl radicals usually occurs. Complete suppression of decarboxylation is achieved only when p-benzoquinone is present at such a high concentration that it is effectively the solvent for the reaction.The benzoyloxy- and phenyl semiquinones show marked differences in reactivity, the former tend to combine to form dibenzoyloxy dibenzoquinone while disproportionation is favoured by the latter to form quinhydrone of monophenylbenzoquinone.At lower quinone ratio, the peroxide undergoes induced decomposition by phenyl radicals both in “reactive” and “unreactive” solvents. The induced decomposition involves the formation of radical intermediates which undergo disproportionation, but not intramolecular rearrangement, to form p-phenylbenzoyloxy radicals. The latter can be captured, before undergoing decarboxylation, by the benzoyloxysemiquinones formed in the reaction.A correlation between the electron donating property of a radical and its capability to induce the decomposition of the peroxide was developed.     

Radical-induced aromatic substitution between benzoyl peroxide and benzenediols in the gas phase characterized by mass spectrometry

A radical-induced aromatic substitution mechanism for the reaction between benzoyl peroxide and benzenediols in the gas phase was characterized by mass spectrometry. The benzoyloxy radical produced from the homolysis of benzoyl peroxide associates at its carbonyl group with the phenolic hydroxyl group. The pairing tendency of the unpaired electron on the oxygen of the radical induces electron transfer along the hydrogen bond, which results in the rupture of the O? H bond of the phenol and aromatic substitution at the ortho position of the benzoyloxy radical. Supporting evidence for the mechanism was obtained by isotope labelling.     

Phenol oxidation into catechol and hydroquinone over H-MFI, H-MOR, H-USY and H-BEA in the presence of ketone

Phenol oxidation with hydrogen peroxide into catechol (CL) and hydroquinone (HQ) over H-MFI, H-MOR, H-USY and H-BEA in the presence of diethylketone was investigated. Among the examined zeolites, large pore zeolites having 12-membered oxygen ring aperture, H-MOR, H-USY and H-BEA, showed higher reaction yield than that having 10-membered oxygen ring aperture, H-MFI. The reaction yield over these zeolites was in the order of H-BEA>H-USY>H-MOR>H-MFI, thus the superior one was H-BEA in this work. The sum of the reaction yield of CL and HQ based on hydrogen peroxide was >89% over H-BEA (SiO₂/Al₂O₃=150) in the presence of diethylketone at 373 K for 5 min reaction.     

过氧化苯甲酰的光敏电荷转移分解反应及引发甲基丙烯酸甲酯的聚合

The mechanism of photosensitized decomposition of benzoyl peroxide by several anthracene derivatives has been studied. It comfirms that the photosensitized process is carried out by electron transfer.It is discovered that benzoyl peroxide can be decomposed by sensitizer of different anthracene derivatives which are used either electron donor or acceptor and the active radical which produces in this reaction can initiate the polymerization of MMA. It is considered that the BPO with positive charge in the charge transfer complex is easier to decompose into radical than that with negative charge,so the rate (Rp) of polymerzation of MMA in-itiated by the system of DCA/BPO has higher value than others.     

过氧化苯甲酰的光敏电荷转移分解反应及引发甲基丙烯酸甲酯的聚合

过氧化苯甲酰(BPO)的光诱导分解曾为许多工作者所注意。Walling和Gibian认为:以二苯酮为敏化剂时,BPO的敏化光解是通过三重态的能量转移过程。Encinas和Lissi则认为敏化是通过单重激发态使激发能转移至过氧化物基态的热振动态,从而导致过氧化物的分解。Tokumarur是最早提出过氧化苯甲酰光敏化诱导分解过程中存在着激基复合物(Exciplex)的可能性。最近他们又进一步研究以BPO为猝灭剂去猝