Benzoyl peroxide, determination

The control chart of Figure 8-16 shows the results of 89 production runs of a cream containing a nominal 10% benzoyl peroxide measured on consecutive days. Each sample is represented by the mean percent benzoyl peroxide determined from the results of five titrations of different analytical samples of the cream. 

To determine the exact peroxide content of benzoyl peroxide (and of other organic peroxides) the following procedure may be employed. Place about 0 05 g. of the sample of peroxide in a glass-stoppered conical flask add 5-10 ml. of acetic anhydride (A.R. or other pure grade) and 1 g. of powdered sodium iodide. Swirl the mixture to dissolve the sodium iodide and allow the solution to stand for 5-20 minutes. Add 50-75 ml. of water, shake the mixture vigorously for about 30 seconds, and titrate the liberated iodine with standard sodium thiosulphate solution using starch as indicator. 

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 ... 

If the rate constant kd for spontaneous decomposition of the initiator is known, the efficiency / of initiation may be determined. (This is a refinement of the molecular weight method set forth in Sec. Ic) The spontaneous decomposition rate of benzoyl peroxide in styrene, according to the work of Swain, Stockmayer, and Clarke is 3.2X10- sec. at 60°C. Hence the efficiency of initiation of the polymerization of styrene by benzoyl peroxide at 60°C is indicated to be about 0.60. 

However, the reaction rate is not uniform. The maximum reaction rate must be known to calculate the area needed for heat exchange. This can and should be determined in a laboratory. For the suspension polymerization of polystyrene at 80°C using 0.5% benzoyl peroxide in an inert atmosphere, the reaction takes 4.5 hr to reach completion and the maximum conversion rate is 20% in 0.5 hr.24 Although... 

The Instantaneous values for the initiator efficiencies and the rate constants associated with the suspension polymerization of styrene using benzoyl peroxide have been determined from explicit equations based on the instantaneous polymer properties. The explicit equations for the rate parameters have been derived based on accepted reaction schemes and the standard kinetic assumptions (SSH and LCA). The instantaneous polymer properties have been obtained from the cummulative experimental values by proposing empirical models for the instantaneous properties and then fitting them to the cummulative experimental values. This has circumvented some of the problems associated with differenciating experimental data. The results obtained show that ... 

The data given below are typical of the polymerization of vinyl phenylbutyrate in dioxane solution in a batch reactor using benzoyl peroxide as an initiator. The reaction was carried out isothermally at 60 °C using an initial monomer concentration of 73 kg/m3. From the following data determine the order of the reaction and the reaction rate constant. Note that there is an induction period at the start of the reaction so that you may find it useful to use a lower limit other than zero in your integration over time. The reaction order may be assumed to be an integer. 

The flow-cell design was introduced by Stieg and Nieman [166] in 1978 for analytical uses of CL. Burguera and Townshend [167] used the CL emission produced by the oxidation of alkylamines by benzoyl peroxide to determine aliphatic secondary and tertiary amines in chloroform or acetone. They tested various coiled flow cells for monitoring the CL emission produced by the cobalt-catalyzed oxidation of luminol by hydrogen peroxide and the fluorescein-sensitized oxidation of sulfide by sodium hypochlorite [168], Rule and Seitz [169] reported one of the first applications of flow injection analysis (FTA) in the CL detection of peroxide with luminol in the presence of a copper ion catalyst. They... 

For example, when benzoyl peroxide is allowed to decompose in the presence of an olefin and iodine a high yield of the olefin dibenzoate is formed And very little carbon dioxide. Since Hammond has shown that the rate of the decomposition is independent of the iodine concentration, the iodine must not participate in the rate-determining initial step. It probably reacts with the benzoyloxy radicals to form benzoyl hypoiodite.U8>11 ... 

C. E. H. Bawn, S. F. Mellish. A Method of Determination of the Rate of Molecular Dissociation in Solution. Parts I and II—The Rate of Dissociation of Benzoyl Peroxide and2,2 -Azo-bis(isobutyronitrile) in Various Solvents. Trans. Faraday Soc. 1951, 47, 1216-1227. 

Saiz, A.I., Manriqne, G.D., and Fritz, R. Determination of benzoyl peroxide and benzoic acid levels by HPLC during wheat flonr bleaching process. J. Agric. Food Chem., 49(1) 98-102, 2001. 

Benzoyl peroxide has been tested for carcinogenicity in mice and rats by administration in the diet and by subcutaneous injection and in mice by skin application. Although no significant increases in tumor incidences were found, the lARC has determined that all of the studies were inadequate for a complete evaluation of carcinogenicity in animals. Two studies indicated that benzoyl peroxide may act as a cancer promoter on mouse skin. ... 

Among a small factory population, two cases of lung cancer were found in men primarily involved in the production of benzoyl peroxide, but they were also exposed to benzoyl chloride and benzotrichloride. Benzoyl peroxide exposure was associated with a greater frequency of malignant melanoma in one of two case control studies it was not associated with basal cell carcinomas of the skin in another study. The lARC has determined that there is limited evidence for the carcinogenicity of benzoyl peroxide in experimental animals and that it is not classifiable as to its carcinogenicity to humans. 

Wheat flour, dibenzoyl peroxide determination, 698, 701 Workplace air benzoyl peroxide, 701 peracetic acid, 699 Wurster s reagent, hydroperoxide determination, 678, 684... 

Copolymerization reactions Copolymerization experiments with styrene and MMA employed molar fractions of 20, 40, 60, and 80% comonomers, which were reacted in ethanol 1,2-dichIorethane 60 40 (by volume) mixtures and benzoyl peroxide as catalyst. Polymerizations were carried out at 70°C. The reactions were quenched by the addition of methanol as non-solvent, and the copolymer was isolated by centrifugation. Copolymer analysis employed UV spectroscopy for copolymers with MMA, and methoxyl content determination according to a procedure by Hodges et al. (16) in the case of styrene copolymers. Reactivity ratios were determined in accordance with the method by Kelen-Tiidos (17) and that by Yezrielev-Brokhina-Roskin (YBR) (18). Experimental details and results are presented elsewhere (15). 

Reactivity ratios between acrylated lignin model compound (Fig. 2), defined as Mi, with either MM A or S, defined as M2, were determined experimentally in accordance with standard procedures (15). These involve mixing two different vinyl monomers in various molar ratios with catalyst (i.e., benzoyl peroxide) and solvent, heating the mixture to achieve polymerization, and recovering the polymer by the addition of non-solvent, and centrifugation. The respective molar monomer fractions of the copolymer were determined by UV-spectroscopy in the cases where MMA served as M2, and by methoxyl content analysis in those cases in which S was the M2-species. The results were subjected to numerical treatments according to the established relationships of Kelen-Tiidos (17) and Yezrielev-Brokhina-Roskin (YBR) (18), and this is described elsewhere (15). 

Materials. GMC and PCLS were synthesized by free radical solution polymerization initiated by benzoyl peroxide as described previously (5,6). Nearly mono and polydisperse polystyrenes were obtained from Pressure Chemical Co. and the National Bureau of Standards respectively. Molecular weight and polydispersity were determined by gel permeation chromatography (GPC) using a Water Model 244 GPC, equipped with a set (102-106 A) of —Styragel columns using THF as the elution solvent. The molecular parameters of the above three polymers are listed in Table I. The copolymer, poly(GMA-co-3-CLS), contained 53.5 mole % 3-CLS and 46.5 mole % GMA, as determined by chlorine elemental analysis. The structure of the copolymer is shown in Figure 1. 

Beckmann rearrangement of, 729,741 p-Benzoquinone, 745 Benzoylacetone, 865 o-Benzoylbenzoic acid, 728, 739 Benzoyl chloride, 791, 792 Benzoyl glycine, 584 Benzoyl peroxide, 807 determination of, 809 Benzoyl piperidine, 489, 492 P-Benzoylpropionic acid, 728, 737 P-Benzoylpropionitrfle, 911, 912 Benzoyl-p-toluidide, 582, 583 Benzyl acetate, 780, 783 Benzylacetophenone, 726, 734 Benzyl alcohol, 706,711, 811,812,884 N-Benzylamid es 394 table of, 395 ... 

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). 

It was also described that some common vinyl polymers, such as polymethyl methacrylate prepared with benzoyl peroxide, are able to initiate a further polymerization if heated in the presence of a second monomer [158). These phenomena must be interpreted by the existence of peroxide links inside the polymethyl methacrylate chain [229). Indeed any activity is destroyed on prolonged heating and this polymer can be used for initiating the polymerization of styrene. However the relative length of the sequences and the molecular weight of the product before and after copolymerization have not yet been determined. 

The reaction mechanism for A-oxidation by performic acid has been studied by AMI calculation methods.174 The iminium salt A-mcthyl-3,4-dihydroisoquinolinium p-toluenesulfonate has been used to catalyse the oxidation of the azo dye calmagite by peracetic acid. The mechanism at pH 10 involves peracid oxidation of the quinolinium ion to form an oxaziridinium salt, which then acts as an oxygen transfer agent for oxidation of cahnagite.175 The presence of lithium salts affects the course of the reaction determining the formation of benzoyl peroxide and benzoic acid as final products in the oxidation of benzaldehyde by perbenzoic acid.176,177... 

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