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.     

Homolytic reactions of polyfluoroaromatic compounds Part VIII. The decomposition of benzoyl peroxide in hexafluorobenzene

The decomposition of benzoyl peroxide in hexafluorobenzene proceeds by a spontaneous first-order process accompanied by an induced decomposition showing 1.5-order dependence upon the concentration of the peroxide. The induced decomposition is associated with the formation of 2,2′,3,4,5,6-hexafluorobiphenyl and benzoic acid. 2,3,4,5,6-Pentafluorobiphenyl is the main product at all concentrations of peroxide; small amounts of other compounds are formed, together with a high-boiling residue probably containing isomeric dodecafluorotetrahydroquaterphenyls. The mechanism is discussed.     

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.     

Thermal decomposition of solid benzoyl peroxide in the presence of solid admixtures: Part I. Observations made under constant heating conditions

The effect of some solid admixtures on the decomposition of benzoyl peroxide in the solid state has been observed by means of differential enthalpic analysis. Admixtures which either might well participate in the radical chain process or only dilute the given reaction system have been chosen. These have been various kinds of carbon black differing from each other by free-spin concentration, chain structure and surface area, further activated charcoal and colloid silica, respectively.     

Comparison of isothermal and non-isothermal chemiluminescence and differential scanning calorimetry experiments with benzoyl peroxide

Difference in the kinetics of chemiluminescence (CL) and differential scanning calorimetry records for decomposition of originally solid benzoyl peroxide continuing as a melt reaction was outlined. While the main portion of heat measured by DSC is released in the spontaneous decomposition of benzoyl peroxide starting as a homolytic scission of peroxidic bonds, the CL light emission in oxygen comes presumably from the subsequent disproportionation reaction of polyphenyl peroxyl radicals and monitors the induced decomposition of peroxide. Thermogravimetry revealed that oxygen remains partially bound to the products of benzoyl peroxide decomposition.     

Network formation of a phenyl vinyl ketone copolymer with 4-vinylbenzil and its photodecrosslinking in films

The irradiation (λ > 400 nm) in air of a copolymer of phenyl vinyl ketone with 4-vinylbenzil (VBZ) containing 1.5 wt % VBZ structural units in film, followed by the thermal decomposition of the resulting pendant benzoyl peroxide groups, leads to crosslinking. The subsequent irradiation of the crosslinked polymer at 366 nm results in the cleavage of the poly(phenyl vinyl ketone) chain between the junction points of the polymer network through a Norrish type II reaction. Therefore, poly(phenyl vinyl ketone-co-4-vinylbenzil) represents a novel type of photoresist based on polymer network decrosslinking. The process involves three steps: photogeneration of peroxide, crosslinking by its thermal decomposition, and subsequent photodecrosslinking of the polymer network. This material provides positive-tone images after UV exposure (λ > 330 nm) and development in an organic medium such as isopropyl methyl ketone. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 765–771, 2004     

Catalytic and inhibiting effects of ferrocene on the bulk radical–coordination polymerization of methyl methacrylate from the standpoint of formal kinetics

The kinetic curves and rates of bulk radical–coordination polymerization of methyl methacrylate initiated by the benzoyl peroxide–ferrocene system at 293–373 K, initial benzoyl peroxide concentrations of 10^–4–10^–1 mol/L, and a constant initial ferrocene concentration of 10^–3 mol/L have been calculated using a mathematical model in which the process is considered from the standpoint of formal kinetics. The calculations have demonstrated that, at low methyl methacrylate conversions, ferrocene catalyzes the process at any benzoyl peroxide concentration; at medium and high methyl methacrylate conversions, deficient amounts of ferrocene with respect to benzoyl catalyze the process as well, while excess ferrocene inhibits the process. The observed effect is explained by the specific ferrocene–benzoyl peroxide interaction, which, depending on the ferrocene: benzoyl peroxide ratio, either increases or decreases the concentration of radicals in the reaction mass.     

The Role of a Metallocene Additive in Radically Initiated Polymerization when Solving Direct and Inverse Kinetic Problems

Polymerization of methyl methacrylate, initiated by benzoyl peroxide in the presence of titanocene dichloride, is considered from the point of view of formal kinetics. Based on the kinetic scheme of the process (which includes the reactions of classical radical polymerization, the reaction of benzoyl peroxide with titanocene dichloride, the reactions of the controlled radical polymerization of organometallic mediated radical polymerization (OMRP) and atom transfer radical polymerization (ATRP), the reaction of the formation of a coordinating active site and the coordinating chain propagation on a mathematical model of the kinetics of the process is created. This model also makes it possible to calculate the molecular-mass characteristics of poly(methyl methacrylate). As a result of the solution of the inverse kinetic problem at a temperature of 343 K, the values of the reaction rate constants of the kinetic scheme are found under which the discrepancy between the calculated models and experimental data is minimal. Using the developed model of the kinetics of the process, a numerical experiment is performed (i.e., a direct kinetic problem is solved). This problem revealed the following regularities of the process. (1) An increase in the initial concentration of titanocene dichloride at a constant initial concentration of benzoyl peroxide leads to an increase in the rate of consumption of benzoyl peroxide but not to an increase in the initial rate of the process compared to classical radical polymerization. (2) With an increase in the initial concentration of titanocene dichloride, the lifetime of the macroradicals at the initial stage of the process is reduced, and hence the molecular weight of the resulting polymethyl methacrylate is less than that of the polymethyl methacrylate obtained in the absence of titanocene dichloride, and it will increase during the process of approaching the final values. (3) During the polymerization of methyl methacrylate, initiated by benzoyl peroxide in the presence of titanocene dichloride, a smoothing gel effect (as in the case of the polymerization of methyl methacrylate initiated by benzoyl peroxide in the presence of ferrocene) does not occur since titanocene dichloride forms stable complexes with methyl methacrylate and, consequently, it participates in reactions consuming macroradicals to a lesser degree than ferrocene.     

Metallocene catalysis in the complex-radical polymerization of methyl methacrylate

The initiation stage of methyl methacrylate polymerization in the presence of benzoyl peroxide-metallocene (MC) systems is considered, with MC = Cp₂Fe, (C₅Me₅)₂Fe, (AcC₅H₄)(C₅H₅)Fe, Cp₂TiCl₂, Cp₂ZrCl₂, and (C₅Me₅)₂ZrCl₂. The decomposition of benzoyl peroxide in the presence of a metallocene proceeds via the formation of its complex with the metallocene. The catalytic effect of the metallocenes on the initiation of methyl methacrylate polymerization is due to the formation of a metallocene-benzoyl peroxide complex and its decomposition yielding primary radicals. The chain propagation stage is metallocene-dependent, which is explained by the formation of complex sites. Their formation pathway and structures are analyzed using quantum-chemical calculations.     

Kinetic Features of Decomposition of Benzoyl Peroxide in Superbasic Media

Kinetics of decomposition of benzoyl peroxide in superbasic media comprising mixtures of a dipolar aprotic solvent and a strong ionic base is studied. The process occurs in two steps through formation of intermediate perbenzoate anion. The contribution of ionic reactions is controlled by the polarity and dielectric constant of the solvent. The decomposition products are molecular oxygen and an alkali metal benzoate or perbenzoate. These products can be alkylated with butyl bromide in superbasic media.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 5, 2005, pp. 803–808.Original Russian Text Copyright © 2005 by Lyavinets.     

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。     

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     

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.     

A chemiluminescence and fluorescence spectroscopy study: An investigation of photocrosslinking processes in polymer systems

Chemiluminescence emission is shown to be a valuable method for the analysis and monitoring of the photochemical transformation process in BZMA-co-S copolymers. BZMA-co-S copolymer films are synthesized and irradiated at λ > 400 nm, in order to induce the phototransformation of benzyl (BZ) to benzoyl peroxide (BP) pendant groups, resulting in thermal decomposition and crosslinking. The chemiluminescence emission increases with irradiation time, and is shown to be related to the benzoyl peroxide moieties generated during irradiation. The increase in chemiluminescence intensity is interrupted at longer periods of irradiation, when the concentration of these species tends to a nearly constant value. In this case, others factors are considered to influence the chemiluminescence emission, for example the increasing crosslinking on irradiated samples, which would restrict the mobility of radicals to recombine due to crosslinking of the network.A good correlation between fluorescence, FTIR and CL measurements during photochemical formation and thermal decomposition of peroxides is found. In this work, an intramolecular excimer forming fluorescent probe, DiPyM, is also used to analyse the crosslinking process. The results obtained contribute significantly to the development of chemiluminescence as a highly sensitive methodology for assessing the photocrosslinking of a polymeric material in the early stages of the process and is due to its sensitivity in comparison to that of fluorescence analysis.     

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.     

Determination of rate constants of benzoyl peroxide and azobisisobutyronitrile dissociation via polymerization kinetics

A linear expression is derived from Tobolsky's equation related to the dead-end polymerization method to determine the rate constant for the initiator dissociation. This novel graphical method applies remarkably well to the kinetic data collected by dilatometry from the polymerization of methyl methacrylate initiated by 2,2′-azobisisobutyronitrile and benzoyl peroxide in toluene at 60°C. Results obtained for these two initiators are consistent with those published in the literature. Applicability of the method is confined to at least 5% and at most 13% decomposition of initiator. However, these limiting values are sensitive to the experimental techniques employed. The effects of induced decomposition of benzoyl peroxide and thermal polymerization of methyl methacrylate are shown to be negligible in the present investigations.     

Chemiluminescence method for determination of benzoyl peroxide in solution

The chemiluminescence reaction of benzoyl peroxide with triethylamine is used to quantify benzoyl peroxide. The method is rapid with a detection limit for benzoyl peroxide in chloroform of 0.07 μg ml^?1 and a relative standard deviation of 4% at 1 μg ml^?1. The technique is applied to the determination of benzoyl peroxide in pharmaceutical preparations.     

Photodegradation of Poly[methyl(phenyl)silylene] in the Presence of Modifying Substances

Summary: Efficiency of the photodegradation of poly[methyl(phenyl)silylene] can be increased by electron acceptor additives with unstable anion radicals. The best chain degradation yield was obtained using benzoyl peroxide as an additive. The model for the photodegradation process is supported by quantum chemical calculations.     

Adsorption and decomposition of diacylic peroxides on the surfaces of dispersed oxides

The adsorption of oligo(sebacoyl peroxide) on Aerosil and MgO and benzoyl peroxide on Fe₂O₃, Cr₂O₃, and V₂O₅ has been studied. It has been established that peroxide adsorption on the considered adsorbents is described by the Langmuir equation. Benzoyl-peroxide adsorption increases in the series Fe₂O₃ < Cr₂O₃ < V₂O₅. The process of thermal decomposition of peroxides in the presence of the listed adsorbents has been studied. The overall reaction of peroxide decomposition comprises two components, i.e., the decomposition processes occurring in a solution and on an adsorbent surface. Kinetic and activation parameters of the thermal-decomposition reactions in the solutions and on the surfaces have been determined.