Synthesis of 4-tert-butylperoxy-4-methylpentan-2-one and 3-tert-butylperoxy-3-methylbutanoic acid

Alkylation of tert-butyl hydroperoxide with 1,3-diols gave the corresponding hydroxy-containing ditertiary peroxides which were oxidized with pyridinium chlorochromate to carbonyl-containing peroxides. 3-tert-Butylperoxy-3-methylbutanal was oxidized with oxygen at room temperature to obtain 3-tert-butylperoxy-3-methylbutanoic acid.     

Thermal decompositions of dialkyl peroxides studied by DSC

Studies on the thermal decompositions of diamyl peroxide (DAPO), dicumyl peroxide (DCPO), and tert-butyl cumyl peroxide (TBCP) were conducted by DSC. Heat of decomposition, exothermic onset point, and chemical kinetics were determined and compared to those data of di-tert-butyl peroxide (DTBP), a model compound for studying thermokinetics of organic peroxide and standardization of a calorimeter. Similarities and differences of decomposition mechanisms between these organic peroxides were proposed and verified. Kinetics on decomposition of uni-molecular reaction via these similar alkoxyl radials accompanying β C–C bond scission were discussed and compared to the results from ab initio calculations. The ranking of thermal stability on dialkyl peroxides is determined to be in the following sequence: DCPO < TBCP < DAPO < DTBP. This rate-determining step in thermal decomposition of dialkyl peroxides possessed an average eigenvalue of log A at about 13.1 ± 1.2. Activation energy on the thermal decomposition of these peroxides was calculated to be 139.5 ± 14.4 kJ mol^?1.     

Generation of alkyl radicals from alkylsilyl peroxides and their applications to C-N or C-O bond formations

This article describes a novel method for the generation of alkyl radicals from alkylsilyl peroxides and their applications to the Cu-catalyzed mono-N-alkylation of amides or arylamines, and to the O-alkylation of carboxylic acids. The use of alkylsilyl peroxides as alkyl radical sources includes the following synthetic advantages: i) various alkylsilyl peroxides can be readily synthesized from the corresponding alcohols and be stored at bench, and ii) a variety of alkyl radicals can be generated efficiently under mild conditions.     

Initiating radical polymerization of vinyl monomers by silicon peroxides

The initiating ability of organosilicon peroxides, Me_4-mSi(OOCMe₃)_mwherem = 1−3, for polymerization of vinyl monomers has been quantitatively characterized. Complex formation between monomers and Lewis acids has been found to activate the polymerization process. The activation effect is observed for a ratio [Lewis acid]/[monomer] of 0.003 to 0.02. The complex formation parameters (equilibrium constant and complex composition) have been determined by PMR, thermochemical and cryoscopic methods. Organosilicon peroxides have been found to influence the composition of copolymers; polyfunctional peroxides can be used to prepare block copolymers.     

Synthesis of <Emphasis Type="Italic">tert</Emphasis>-Alkylperoxy-substituted Derivatives of 2-Propanol,Dioxolane, and Thiirane

Treatment of tert-alkyl-2-oxiranylmethyl peroxides with compounds containing an active hydrogen, with ketones, chlorosilanes, and potassium thiocyanate furnished a series of functionally-substituted dialkyl peroxides.     

Photo-stability of photo-cured organic coatings: Part I—Secondary reactions in thioxanthone/amine photo-cured organic coatings

Luminescence measurements on 2-iso-propylthioxanthone (ITX) in a poly(methyl methacrylate) (PMMA) film as a model system were carried out to study the secondary reactions of ITX during and after photocrosslinking of organic coatings. The energy of the lowest excited triplet state (T₁) of ITX was calculated to be E₁₁ = 62·2 kcal/mol. The ITX triplet lifetime in a PMMA film was calculated from the phosphorescence decay to be τ = 1·0 ms. Irradiation of a PMMA film containing 4 mm ITX resulted in rapid photoreduction of the aromatic ketone. In a PMMA-benzene solution, studied for comparison, the photo-reduction rate was lower than in film. Triplet excited ITX may decompose peroxides by an energy transfer process. As the model system a mixture of tert-butylhydroperoxide and di-tert-butylperoxide was irradiated with uv light in the presence of ITX in benzene solution. This was found to give tert-butoxy radicals. The same radicals were formed by irradiation of a PMMA sample containing peroxides. The radicals formed were identified and measured using ESR spectroscopy combined with the spin trapping technique. The investigations reported here have established evidence for two important secondary reactions in the photo-curing of organic coatings using thioxanthone/amine as the initiating system: photo-reduction of ITX by hydrogen abstraction from the polymer and photo-decomposition of peroxides and hydroperoxides sensitized by thioxanthone.     

Influence of imidazole on the kinetics of oxidation of 5,15-di(<Emphasis Type="Italic">ortho</Emphasis> -methyloxyphenyl)-2,3,7,8,12,13,17,18-octamethylporphyrin with organic peroxides in <Emphasis Type="Italic">o</Emphasis>-xylene

The structure of zinc 5,15-di(ortho -methyloxyphenyl)-2,3,7,8,12,13,17,18-octamethylporphyrin was studied by spectrophotometry and computer simulation. Its properties in the reaction with organic peroxides in o-xylene in the presence of imidazole were studied at 295 K. The apparent and true rate constants for this process were calculated. The metalloporphyrin chromophore was found to decompose completely during the interaction of the zinc porphyrin (ZnP) with peroxides. The influence of imidazole on the reaction rate was revealed. The geometric characteristics of the optimized ZnP structure and intermediates of the oxidation were obtained by the PM3 quantum-chemical method. The deformational strains in the ZnP macrocycle were found to increase during the reaction.     

Sonoluminescence and sonochemiluminescence of peroxide solutions

Two sonochemiluminescence mechanisms were established in peroxide solutions. The sonochemiluminescence intensity often exceeds the sonoluminescence intensity of solvents caused by inelastic collisions of cavitation bubbles in the gas phase. In solutions of peroxides, whose chemiluminescence decomposition proceeds via the monomolecular peroxide decomposition involving no radical intermediates with a high activation energy, in particular, for adamantylidenadamantane-1,2-dioxetane, the mechanism based on the total thermal ultrasonic action on the solution takes place. The initiation of chemiluminescence reactions of peroxide decomposition by radical products of solvent sonolysis is a source of sonochemiluminescence for peroxides decomposing via the radical mechanism, for example, for cumene peroxide.     

Fe- or co-catalyzed silylation-peroxidation of alkenes with hydrosilanes and T-hydro

The silylation-peroxidation of alkenes with hydrosilanes and T-hydro was developed by using iron or cobalt catalyst. The three-component protocol provided a practical method for synthesis of a variety of β-silyl peroxides. Excellent diastereoselectivity of the silylation-peroxidation of alkenes was achieved when internal alkenes were used.     

Determinations cinetiques par analyse microcalorimetrique differentielle. XV. Thermolyse de peroxydes de benzoyle p,p′-disubstitués en solution dans l'ether de diphenyle

Differential scanning microcalorimetric and chemical studies of the thermolysis of some p,p′-disubstituted benzoyl peroxides have been performed in diphenyl oxide as solvent. They have shown that the decomposition proceeds only via the homolysis of the peroxide bond; neither free radical induced nor autocatalytic processes occur. The activation parameters of the thermolysis of the peroxides have the same values as those found when propiophenone is used as solvent. Under these conditions, the free enthalpy of activation, ΔG^≠, is the intrinsic measure of the thermal stability of benzoyl peroxide and its p,p′-disubstituted derivatives.     

Oxidizing properties of the tert-butyl hydroperoxide-tetra-tert-butoxychromium system

tert-Butyl hydroperoxide reacts with the tetra-tert-butoxychromium by oxidizing the latter to chromyl CrV=O (C₆H₆, 20°C). At t-BuOOH-Cr(OBu-t)₄ ratio of 2: 1 or higher, oxygen is released. The occuring processes include the formation of chromium-containing peroxides and peroxytrioxydes. The t-BuOOH-Cr(OBu-t)₄ system oxidizes aromatic hydrocarbons of various structures (anthracene, 9,10-dimethylanthracene, 1,1-diphenylethylene, alkylarenes), as well as primary and secondary alcohols. Depending on the structure of the substrate, the oxidants are: in situ generated oxygen including that in the singlet state, peroxy radicals, or chromium-containing peroxides.     

Isothermal versus non-isothermal calorimetric technique to evaluate thermokinetic parameters and thermal hazard of tert-butyl peroxy-2-ethyl hexanoate

Liquid organic peroxides have been broadly employed in the process industries such as tert-butyl peroxy-2-ethyl hexanoate (TBPO). This study investigated the thermokinetic parameters of TBPO, a typical liquid organic peroxide, by isothermal kinetic algorithms and non-isothermal kinetic algorithms with thermal activity monitor III, and differential scanning calorimetry, respectively. An attempt has been made to determine the thermokinetic parameters by simulation software, such as exothermic onset temperature (T ₀), maximum temperature (T _max), decomposition (?H _d), activation energy (E _a), self-accelerating decomposition temperature, and isothermal time to maximum rate (TMR_iso). A liquid thermal explosion model was established for a reactor containing liquid organic peroxide of interest. From experimental results, liquid organic peroxides?? optimal conditions for avoiding a violent runaway reaction of storage and transportation were created.     

Reactions of titanium alcoholates Ti(OR)4 (R = n-Bu, t-Bu) with tertiary organic and organometallic hydroperoxides

tert-Butyl and cumyl hydroperoxides in the reactions with Ti(OR)₄ are reduced to alcohols with the evolution of oxygen via formation of titanium-containing peroxides and trioxides. The pathways of the reactions of Ti(OR)₄ with triphenylelement hydroperoxides R₃EOOH (E = C, Si, Ge) depend on element E and on the structure of R; the reactions involve the rearrangement of the peroxides, and with (n-BuO)₄Ti the alkoxy group is oxidized either with preservation or with breakdown of the hydrocarbon skeleton.     

Light emission on heating polymer networks formed by radical polymerization

Organic-inorganic hybrid monomers based on alkoxysilanes bearing methacrylate groups, or the pure organic dimethacrylate monomers were photo-polymerized to densely cross-linked networks. Storage of the polymer samples in nitrogen and at ambient laboratory temperature was associated with a slow decay of trapped free radicals and formation of new cross-links. In air, reactions with oxygen lead competitively to formation of peroxides due to easier diffusion in the polymer matrix. The formation and existence of peroxides in samples stored in air was shown by the chemiluminescence (CL) induced at elevated temperatures. The peroxide accumulation proceeds in three stages. At first, approximately up to 6 weeks, a high rate of accumulated peroxides activated by long living radicals is assumed. During the next 20 weeks a steady state oxidation stage is observed before another accumulation of peroxides occurs. The glass transition temperature (T_g) changes were used to estimate variation of cross-link density during ageing the networks. As far as the entirely organic network is concerned the main portion of precursors giving rise to cross-links in the post-curing period was deactivated within 9 weeks under the influence of oxygen. Contrary to this finding in networks based on organic-inorganic hybrid monomers and a copolymer of the inorganic and organic monomers the additional cross-linking is considerably less influenced by oxygen. It is anticipated that a pronounced network structure favours further cross-linking over oxygen addition.     

Differential scanning calorimetry study of the thermal decomposition of peroxides in the absence of a solvent

The thermal decompositions of benzoyl peroxide (Bz₂O₂), dicumyl peroxide (DICUP) and α, α′-bis (t-butylperoxy)m/p-diisopropylbenzene (Peroximon F) in the absence of solvents have been studied by means ofDSC alone. The DSC curves allowed calculation of the half-lifetime (t _1/2) and the time (t ₁) required to decompose the whole of the peroxides. Thet ₁, andt _1/2 values found for the pure peroxides are lower than those in the literature for decomposition in solution. The heat of decomposition and the activation energy for each peroxide are reported.     

A contribution to the volumetric electrometric determination of some organic peroxides in alkaline media

Conditions for the determination of DBP, CHP, MEKP, and MCHP, as well as m-chloroperbenzoic acid, with a standard solution of SnII-glyc or SnII-sorb by the potentiometric, bipotentiometric, and biamperometric method were found. Quite good results were obtained in comparison with individual modifications of the iodometric method. Large positive errors were found only for the determination of m-chloroperbenzoic acid with SnII-glyc. The reductometric procedure is an advantage in the determination of organic peroxides by this procedure.     

The analysis of combustion products : The effect of hydrogen peroxide on the reaction of potassium permanganate with organic peroxides in acid solution

Although methyl and ethyl hydroperoxides alone do not react with potassium permanganate in acid solution at room temperature, they can be oxidised by this reagent in the presence of hydrogen peroxide. The apparent equivalents (as compared with hydrogen peroxide) are much lower than usual but, in the presence of excess hydrogen peroxide, the titre due to the organic peroxide is proportional to its original concentration. This forms the basis of a simple titration method which, though empirical, is both rapid and accurate. Since t-butyl hydroperoxide does not react in this way, it may be possible to differentiate the higher peroxides from lower peroxides.     

Synthesis of triterpenoid-based 1,2,4-trioxolanes and 1,2,4-dioxazolidines by ozonolysis of allobetulin derivatives

Oxidation of allobetulin derivatives with ozone results in good isolated yields of 1,2,4-trioxolanes and stable 1,2,4-dioxazolidines. Individual 3R,5R and 3S,5S diastereoisomers of allobetulin secondary ozonides were isolated and their structures confirmed by X-ray crystallographic analysis. Remarkable diastereoselectivity with formation of only the (3S,5S)-configured peroxides was observed during the oxidation of 1,5-di-O-methoxyoximinoallobetulin to dioxazolidines.     

Study of intermolecular interaction of Mg-5,15-Di(o-methoxyphenyl)-2,8,12,18-tetramethyl-3,7,13,17-tetrabutylporphin with o-xylene organic peroxides. Effect of imidazole on the reaction kinetics

Using the method of spectrophotometric titration a reaction of magnesium porphyrinate with the o-xylene organic peroxides was investigated, the reaction mechanism and kinetic parameters were determined. The effect of imidazole on the rate of the reaction under investigation was demonstrated. The presence of steric strain in the magnesium porphyrinate macrocycle and its increase in the course of formation of intermediates was observed.     

Trunculins X and Y from an Okinawan sponge Sigmosceptrella sp.

Two new norsesterterpenoid cyclic peroxides, trunculins X and Y, were isolated from an Okinawan sponge Sigmosceptrella sp. Their structures were determined by spectroscopic analyses on intact molecules and derivatives and also by crystallographic study. The compounds showed cytotoxicity in a range of IC₅₀ 0.32–20 μM against three cell lines.