Di-benzoyl peroxide

Willson (8) also studied the degradation of di-benzoyl peroxide using isothermal microcalorimetry. Literature values for the degradation of di-benzoyl peroxide at 100°C are 3.8 x 10 4 s 1 with an activation energy of... 

Table 8 Reaction parameters determined for the degradation of di-benzoyl peroxide at 25°C by fitting microcalorimetric data to the Ng equation (8)...

Zur Dehydrierung von l,4-Bis-[2,3-dihydro-l,3-benzothiazol-2-yl]-benzol wird mit 2,67 Aquivalenten Di-benzoyl-peroxid (30 min bei 0° danach 1 h bei 25°) geriihrt, der Niederschlag abfiltriert und mit Chloroform gewaschen. Man erhalt 1,4-Bis-[l,3-benzothiazol-2-yl]-benzol (Schmp. 262-264°) zu 80%. 

FIGU RE 2.3 Typical initiators in radical polymerization A = AZDN B = Di benzoyl peroxide C = T-butyl perbenzoate D = Di f-butyl peroxide. 

However, ti for any given initiator does not only depend upon the reaction temperature, but also upon the reaction environment, and the concentration of initiator present. This can be illustrated by the following example for di-benzoyl peroxide. 

Copolymers of diallyl itaconate [2767-99-9] with AJ-vinylpyrrolidinone and styrene have been proposed as oxygen-permeable contact lenses (qv) (77). Reactivity ratios have been studied ia the copolymerization of diallyl tartrate (78). A lens of a high refractive iadex n- = 1.63) and a heat distortion above 280°C has been reported for diallyl 2,6-naphthalene dicarboxylate [51223-57-5] (79). Diallyl chlorendate [3232-62-0] polymerized ia the presence of di-/-butyl peroxide gives a lens with a refractive iadex of n = 1.57 (80). Hardness as high as Rockwell 150 is obtained by polymerization of triaHyl trimeUitate [2694-54-4] initiated by benzoyl peroxide (81). 

Cationic polymerization of tetrahydrofuran with the or bis(3,5-di-bromomethyl) benzoyl peroxide and AgPp6 pairs of 4,4 -bromomethyl benzoyl peroxide and AgPp6 yield active poly-THP having peroxide group in the main... 

The polymerization of vinyl monomers on the surface of silica can be induced also by free radical initiators such as azo-bis-isobutyronitrile (AIBN), di-tert-butylperoxide, benzoyl peroxide etc. The selection of initiator type and method of its introduction in polymerizable systems are determined by the nature of monomers and tasks of investigations. Usually, the following procedures are used ... 

In order to bring about crosslinking of polyesters with styrene one of two types of initiator systems is used, which differ in the temperature at which they are effective. For curing at elevated temperatures, peroxides are used which decompose thermally to yield free radicals. Among those peroxides employed are benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, di-t-butyl peroxide, and dodecyl peroxide. Mixtures of polyester prepolymer, styrene, and such initiators are reasonably stable at room temperatures but undergo fairly rapid crosslinking at temperatures between 70 °C and 150 °C, depending on which particular peroxide is used. 

The liquids used were 1 1 mixtures of EBA-HV and liquid methacrylate which also contained dihydroxyethyl-p-toluidine as the accelerator. Both mono- and di-methacrylates were used. The benzoyl peroxide initiator was included in the EBA zinc oxide/silanized (1 1) glass powder. These polymer cements set 5 to 10 minutes after mixing. Since there is a substantial amount of monomer in the liquid (50%) the contribution of the polymer to the strength of the cement must be considerable. Brauer Stansbury (1984b) suggested that the two matrices, the polymer matrix and the salt matrix, may be interpenetrating but separation of the two phases is likely. 

The reductive elimination of a variety of )3-substituted sulfones for the preparation of di-and tri-substituted olefins (e.g. 75 to 76) and the use of allyl sulfones as synthetic equivalents of the allyl dianion CH=CH—CHj , has prompted considerable interest in the [1,3]rearrangements of allylic sulfones ". Kocienski has thus reported that while epoxidation of allylic sulfone 74 with MCPBA in CH2CI2 at room temperature afforded the expected product 75, epoxidation in the presence of two equivalents of NaHCOj afforded the isomeric j ,y-epoxysulfone 77. Similar results were obtained with other a-mono- or di-substituted sulfones. On the other hand, the reaction of y-substituted allylic sulfones results in the isomerization of the double bond, only. The following addition-elimination free radical chain mechanism has been suggested (equations 45, 46). In a closely related and simultaneously published investigation, Whitham and coworkers reported the 1,3-rearrangement of a number of acyclic and cyclic allylic p-tolyl sulfones on treatment with either benzoyl peroxide in CCI4 under reflux or with... 

The inhibited unimolecular decomposition of symmetrically di-substituted benzoyl peroxides into radicals also obeys the Hammett rho-sigma relationship. Unfortunately, no extensive activation parameter data are available. The effect of the substituent changes on the rates at the single temperature has been explained in terms of dipole-dipole repulsion in the peroxide.122... 

All four polymerization processes can be used to make PS. The reaction is an addition polymerization using a free radical initiator (benzoyl peroxide or di-tertiary butyl peroxide). Mostly, the suspension or bulk processes are... 

The various initiators are used at different temperatures depending on their rates of decomposition. Thus azobisisobutyronitrile (AIBN) is commonly used at 50-70°C, acetyl peroxide at 70-90°C, benzoyl peroxide at 80-95°C, and dicumyl or di-t-butyl peroxide at 120-140°C. The value of the decomposition rate constant kj varies in the range... 

Phenylation of quinoline with benzoyl peroxide is easier (qpl,nR 5.0) than that of pyridine (71BSF2612). Substitution takes place at all carbons, and partial rate factors (F2 = 3.3, F3 = 1.8, F4 = 5.4, Fs = 6.6, F6 = 1.5, F7 = 1.6, F8 = 9.6) were obtained at 1% conversion. Homolytic arylation of quinoline is not of much synthetic value as reactions taken to higher conversion suffer not only from lack of selectivity, but di- and poly-substitution also take place. 

Because of its chemical inertness, no direct way of curing poly(thiocarbonyl fluoride) has been found. However, creep has been reduced and strength at elevated temperatures improved by milling into the polymer a free-radical generator, such as dicumyl peroxide or azobisisobutyronitrile, and a free-radical acceptor, such as N,N -m-phenylenebismaleimide or triacryloylhexahydro-s-triazine, and curing with heat and pressure (65). A better method is to mill in divinylbenzene and a small amount of benzoyl peroxide and cure with heat and pressure (66). The divinylbenzene forms a crosslinked matrix that mechanically traps poly(thio-carbonyl fluoride) molecules. Since the elastomer is in effect filled with poly(di-vinyl benzene), the final composition is less resilient than untreated poly(thio-carbonyl fluoride). 

In general, there are two distinctively different classes of polymerization (a) addition or chain growth polymerization and (b) condensation or step growth polymerization. In the former, the polymers are synthesized by the addition of one unsaturated unit to another, resulting in the loss of multiple bonds. Some examples of addition polymers are (a) poly(ethylene), (b) poly(vinyl chloride), (c) poly(methyl methacrylate), and (d) poly(butadiene). The polymerization is initiated by a free radical, which is generated from one of several easily decomposed compounds. Examples of free radical initiators include (a) benzoyl peroxide, (b) di-tert-butyl peroxide, and (c) azobiisobutyronitrile. 

The graft copolymerization of acrylonitrile onto polystyrene was attempted using benzoyl peroxide, di-/-butylperoxide, and 2,5-dimethyl-2,5-di-(/-butylperoxy)hexane as initiators. In all cases no increase in mass of the polystyrene was observed. Attempts were also made to test whether the polystyryl radical was ever formed by combining the initiator and the polymer or the initiator, polymer and a nitroxide radical trap. In the first case the formation of a radical must lead to cross-linking of the polymer and in the second case the polystyryl radical will be trapped by the nitroxide. ... 

The solution of l,2 5,6-di-0-isopropylidene-a-i>-glucofuranose-3-0-(pentafluorophenyl)-thionocarbonate) [Eq. (10)] 31 (0.195 g, 0.4 mmol) and dimethyl phosphite (0.18 mL, 2 mmol) in dioxane (3 mL) under argon was treated with 150 p,L of benzoyl peroxide solution (0.387 g of benzoyl peroxide in 3 mL of dioxane) four times at 30-inin intervals and under reflux. After evaporation of solvent, the residue was analyzed by NMR to give 100% of the deoxy product 30. 

Lithium dispersion (0.5% sodium in mineral oil, Aldrich) is washed with hexane to remove the oil before use and dried by passing a stream of nitrogen over it. Di-tert-butyldichlorosilane is commercially available (Huls, bp 191°C) or can be prepared by chlorination of di-tert-butylchlorosilane (benzoyl peroxide in refluxing carbon tetrachloride for 8 h, yield > 90%). trans-Butene is commercially available (Aldrich) in lecture bottles and is used as is. Tetrahydrofuran is freshly distilled under nitrogen from sodium ketyl benzophenone immediately prior to use. 

Deoxygenation of esters. Esters can be reduced to hydrocarbons by (QH5)3SiH in the presence of a radical generator, di-f-butyl peroxide, at 140°. Highest yields are obtained with acetates yields based on the alcohol decrease in the order secondary > primary > tertiary. Other silanes are much less effective than triphenylsilane, which is required in excess for high yields. Radical initiators such as AIBN or benzoyl peroxide are not useful.1... 

Bis(dinitrobenzoyl) peroxide. See Di(dinitro-benzoyl)-peroxide under Dibenzoylperoxide... 

The stability of org peroxides (such as acetyl benzoyl peroxide) is greatly increased by prepg a soln of the peroxide in at least 25% by wt of the esters of phthalic acid (such as di-Me or de-Et phthalate)] 14)H-A. Aaronson, "Desensitization of High Explosives by Waxes, Semi-Plastic RDX Compositions , PATR 1761 (1950) (A number of commercially... 

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