Benzoyl peroxide removal

Scratch resistance of polymer from DADC is improved by novel mixtures of peroxide initiators such as 5% isopropyl percarbonate with 3.5% benzoyl peroxide (16). In order to force completion of polymerization and attain the best scratch resistance in lenses, uv radiation is appHed (17). Eyeglass lenses can be made by prepolymerization in molds followed by removal for final thermal cross-linking (18). 

Vinyl acetate [108-05-4] M 86.1, b 72.3 , d 0.938, n 1.396. Inhibitors such as hydroquinone, and other impurities are removed by drying with CaClj and fractionally distilling under nitrogen, then refluxing briefly with a small amount of benzoyl peroxide and redistilling under nitrogen. Stored in the dark at 0 . 

Suspension polymerisation of styrene is widely practised commercially. In this process the monomer is suspended in droplets 5 -Min. in diameter in a fluid, usually water. The heat transfer distances for the dissipation of the exotherm are thus reduced to values in the range s-fisin. Removal of heat from the low-viscosity fluid medium presents little problem. The reaction is initiated by monomer-soluble initiators such as benzoyl peroxide. 

B. 2H-Pyran-2-one. A mixture of 9.81 g. (0.100 mole) of 5,6-dihydro-2/I-pyran-2-one, 200 mg. of benzoyl peroxide, 18.6 g. (0.105 mole) of A-bromosuccinimide [2,5-Pyrrolidinedione, 1-bromo-] (Note 7), and 800 ml. of carbon tetrachloride is prepared in a 2-1., three-necked, round-bottomed flask equipped with a reflux condenser and a mechanical stirrer. The resulting suspension is stirred and heated to reflux. After 1.5 hours at reflux, most of the solid is dissolved, and the solution gives a negative test with starch-iodide paper. The reaction mixture is then allowed to cool, dining which time succinimide [2,5-Pyrrolidine-dione] crystallizes out. The precipitate is removed by filtration, and the filtrate is concentrated under reduced pressure to leave crude 5-bromo-5,6 -dihy dro 211 -pyran-2 one [ 211 Py ran - 2-one, 5-bromo-5,6-dihydro] as an oil. 

Acne medicines may contain ingredients such as salicylic acid, benzoyl peroxide, and sulfur, which remove the top layer of dead skin. They may also contain ingredients that have antibacterial action. Some ingredients reduce sebum production others reduce inflammation. 

Benzoyl peroxide can help remove dead skin cells, which in turn prevents the pores from clogging up. It also kills the Propionibac-terium acnes bacterium that causes acne. It has anti-inflammatory effects and reduces oxygen free radicals and fatty acids on the skin. 

Isopropenyl acetate and allyl chloride behave similarly. In the polymerization of the latter monomer degradative chain transfer occurs more readily by removal of the chlorine atom to yield the unsubstituted allyl radical CH2—CH—CH2, which manages to add monomer occasionally. This is indicated by the formation of about three polymer molecules, having an average degree of polymerization of six units, for each molecule of benzoyl peroxide decomposing. 

The synthesis for each differs only in the relative proportion of monomer loaded into the reaction vessel. Commercial benzoyl peroxide (1 percent by weight based on the sum of TBTM and MMA) was employed as the initiator. 0.8 mol of TBTM freshly recrystallized from ether and 0.8 mol MMA were added to 860 g of benzene in a flask equipped with a thermometer and reflux condenser. To this mixture was added 4.3 g (0.018 mol) of benzoyl peroxide. The flask and contents were warmed at the reflux temperature of benzene (80.1°C) with stirring. After 24 hours reaction time the benzene was removed in vacuo at 50°C. 

The oxidation of hexahydroindolo[2,3-a]quinolizin (574) with benzoyl peroxide, followed by reduction and removal of the benzoyl group, gave the cis alcohol (575), while hydroboration-oxidation of the same enamine (574) yielded... 

Caution This reaction should he carried out behind a safety screen. The solvent removal and product distillation steps should also he carried out behind a screen to minimize trouble if the product is contaminated with undetected peroxides. Benzoyl peroxide should be handled with caution because it is impact-sensitive. 

The monomer addition scheme, shown at the top, requires an initiator which is capable of removing a hydrogen atom from the allylic position of the butadiene, resonance stabilization of the radical from AIBN does not permit this initiator to effect this reaction while benzoyl peroxide is capable of reaction to remove a hydrogen atom and initiate the reaction. On the other hand the polymeric radical addition scheme requires that homopolymerization of the monomer be initiated and this macroradical then attack the polymer and lead to the formation of the graft copolymer. Huang and Sundberg explain that the reactivity of the monomer... 

Both of the above approaches employed a metal ion as a template about which the corrin cyclization was performed, but the nickel or cobalt ions could not subsequently be removed. In order to obtain metal-free corrins, a new route was therefore devised (67AG865) which employed the novel principle of sulfide contraction (Scheme 22). Thus the sodium salt of the precorrin (284) (Scheme 23) was transformed into the thiolactam (285), and loose complexation with zinc(II) ions caused cyclization to give (286), which was treated with benzoyl peroxide and acid to give the ring-expanded compound (287). Contraction with TFA/DMF gave the corrins (288) and (289), and the major of these (289) was desulfurized with triphenylphosphine and acid to give (288). Finally, demetallation with TFA gave the required metal-free corrin (290), a source for a whole variety of metal derivatives. 

A mixture of methyl (2-methylphenyl)acetate (46 82.0 g, 0.5 mmol), NBS (89.0 g, 0.5 mmol), benzoyl peroxide (1.0 g), and CC14 (800 mL) was heated under reflux for 2h while irradiating with a 750 W light source. The precipitated succinimide was then filtered off, the solvent removed, and the residue distilled under reduced pressure to give 43 yield 90.1 g (74%). 

To a solution of 40 g (1.0 moles) of sodium hydroxide in 500 ml of methanol was added 242 g (l.Omoles) of 2.6-dichloro-4-bromophenol. The pH was adjusted between 9.0 and 10.0 (preferably 9.5) by means of one or another of the reactants. The pH was determined by diluting a 2.5 g aliquot with 100 ml of 50% aqueous methanol. The alcohol and water were removed by distillation, fn a one liter round bottom flask there was introduced 100 g of the sodium salt of 2.6-dichloro-4-bromophenol, 350 ml of chlorobenzene and 40 ml of N,N-dimethylformamide. The mixture was agitated until the salt was in solution then immediately there was added 26 ml of dimethylsulfoxide. A suspension forms. The air was removed by alternate evacuation and introduction of nitrogen then there was added 1.0 g of benzoyl peroxide dissolved in 10 ml of toluene. The mixture was stirred for 80 min at 29—33° C then for 5 hours at 54—59° C. The formation of polymer was indicated by the disappearance of the particles of the suspension and an increase in the viscosity of the solution. The polymer was isolated by precipitation into acetone. After filtration the polymer was washed thoroughly with water, then with acetone and then dried at 100° C. There was obtained 60 g (theoretical) of poly-(2.6-dichloro-1.4-phenylene ether). 

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. 

Exercise 29-15 Polymerization of methyl 2-methylpropenoate with benzoyl peroxide labeled with 14C in the aromatic ring gives a polymer from which only 57% of the 14C can be removed by vigorous alkaline hydrolysis. Correlation of the 14C content of the original polymer with its molecular weight shows that, on the average, there are 1.27 initiator fragments per polymer molecule. Write mechanism(s) for this polymerization that are in accord with the experimental data, and calculate the ratios of the different initiation and termination reactions. 

I Materials, Double distilled water and absolute ethanol were used in all polymerisations Styrene monomer was washed with 10% w/w aqueous sodium hydroxide solution and then distilled under a nitrogen atmosphere with reduced pressure to remove inhibitor and impurities. 4.4f-Azobis (4-cyanovaleric acid) (ADIB), recrystallised from absolute ethanol to remove any peroxide impurities, and benzoyl peroxide (BzP) of reagent grade were utilised. 

A mixture of 2-methyl-5-trifluoromethylbenzothiazole (1 mole-equivalent), N-bromosuccinimide (1 mole-equivalent), carbon tetrachloride (700 ml) and a catalytic amount of benzoyl peroxide (0.2 g) was refluxed under irradiation by an UV lamp for 14 hours. The reaction mixture was cooled to room temperature, filtered to remove the precipitated succinimide and the filtrate was evaporated to dryness. The resulting solid was chromatographed over silica gel to obtain the 2-bromomethyl-5-trifluoromethyl-benzothiazole. 

For peroxide cross-linking, organic peroxides, such as dicumyl, di-t-butyl, and benzoyl peroxides, are used in amounts 1 to 3 phr (parts per hundred parts of rubber). Typical cure cycles are 5 to 10 min at temperatures 115 to 170°C (239 to 338°F), depending on the type of peroxide used. Each peroxide has a specific use. A postcure is recommended to complete the cross-linking reaction and to remove the residues from the decomposition of peroxide. This improves the long-term heat aging properties.62... 

A mixture of methyl xanthate (0.4 mmol) and Bu2POH (dibutylphosphine oxide, 2.0 mmol) in dry dioxane (3 ml) was refluxed under an argon atmosphere, and then a solution of benzoyl peroxide (0.4 mmol) in dioxane (3 ml) was added dropwise to the mixture. After 90 min, the solvent was removed and the residue was chromatographed on silica gel to give the reduction product [22]. 

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