Benzoyl peroxide analysis

Due to the low solubility of the monomer 1III) in benzene, the polymerization had to be carried out at less than 10% (w/v) monomer concentration. A yield of 92% was obtained by AIBN initiation at 60°C. Ammonium persulfate and benzoyl peroxide initiators were found to be ineffective. The solubility characteristics of poly(N-pheny1-3,4-dimethylenepyrroline) are listed in Table I. The polymer was insoluble in most common solvents except for formic acid and trifluoroacetic acid. The polymer was characterized by C,H elemental analysis, IR and NMR. 

Literature data for the suspension polymerization of styrene was selected for the analysi. The data, shown in Table I, Includes conversion, number and weight average molecular weights and initiator loadings (14). The empirical models selected to describe the rate and the instantaneous properties are summarized in Table II. In every case the models were shown to be adequate within the limits of the reported experimental error. The experimental and calculated Instantaneous values are summarized in Figures (1) and (2). The rate constant for the thermal decomposition of benzoyl peroxide was taken as In kd 36.68 137.48/RT kJ/(gmol) (11). 

Finally, the use of stable free radical polymerization techniques in supercritical C02 represents an exciting new topic of research. Work in this area by Odell and Hamer involves the use of reversibly terminating stable free radicals generated by systems such as benzoyl peroxide or AIBN and 2,2,6,6-tetramethyl-l-piperidinyloxy free radical (TEMPO) [94], In these experiments, styrene was polymerized at a temperature of 125 °C and a pressure of 240-275 bar C02. When the concentration of monomer was low (10% by volume) the low conversion of PS which was produced had a Mn of about 3000 g/mol and a narrow MWD (PDI < 1.3). NMR analysis showed that the precipitated PS chains are primarily TEMPO capped, and the polymer could be isolated and then subsequently extended by the addition of more styrene under an inert argon blanket. The authors also demonstrated that the chains could be extended... 

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... 

However, it is known, that in homolytical processes certaine influence on reaction rate has also so-called "cage effect", which is described by density of medium cohesion energy. That was confirmed by generalization of data concerning to influence of solvents upon decomposition rate of benzoyl peroxide [2] or oxidizing processes [3, 4], That is why the data analysis from work [1] is seemed as expedient by means of five parameter equation ... 

Treatment of this monomer with benzoyl peroxide gave a high molecular weight polyester by a free radical ring-opening polymerization which can be rationalized by the accompanying scheme. The structure of the polyester IV was established by analysis and hydrolysis as well as infrared and NMR spectroscopy. 

A mixture of 200 mg (2.35 mmol) of methyl cyanoformate and 137 mg (0.566 mmol) of benzoyl peroxide in 10 mL (77 mmol) of 2,3-dimethylbutane is placed in a Pyrex ampoule. After 5.5 h at 99 °C, analysis of the reaction mixture by vPC shows that the nitrile is the only monomeric product yield 77%. 

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. 

The decomposition of the unsymmetrical peroxides (Table 82) does not present anything particularly unusual in rates. The enthalpy of activation for the decomposition of benzoyl phenylacetyl peroxide and phenylacetyl peroxide are similar. An analysis of the products from the decomposition of acetyl benzoyl peroxide in conjunction with kinetic datahaveled Walling and Cekovic to suggest an induced decomposition which is initiated by methyl radical attack on the aromatic ring, viz. 

Analytical pyrolysis can be used successfully for the analysis of end groups in polymers. For example, the pyrolysis of poly(methyl methacrylate) obtained from polymerization with benzoyl peroxide as an initiator shows the presence of characteristic aromatic products in the pyrolysate. Peak intensities in the pyrograms of these characteristic compounds allow the evaluation of initiator levels and the understanding of polymerization mechanism [22],... 

Hatada, K. Kitayama, T. Ute, K. Terawaki, Y. Yanagida, T. End-group analysis of poly(methyl methacrylate) prepared with benzoyl peroxide by 750 MHz high-resolution NMR spectroscopy. Macromolecules 1997, 30, 6754-6759. 

AA, azelaic acid AN, oral antiandrogen blank, N/A BPO, benzoyl peroxide lab, CBC, chem screen, urinalysis OA, oral antibiotic Ol, oral isotretinoin PA, physical assessment PT, pregnancy test SLA, serum lipid analysis TA, topical antimicrobial TR, topical retinoid. 

The commercial (Eastman) benzoyl peroxide may be used if it gives a colorless or pale yellow chloroform solution otherwise it should be recrystallized from a small amount of hot chloroform. It should always be analyzed before use, since the melting point is not a safe criterion of purity. The following method of analysis is convenient and satisfactory ... 

Several methods can be used for the evaluation of the initiator efficiency. One method depends on the direct analysis of initiator fragments as end groups in the polymer formed compared to the amount of initiator consumed. The use of isotopically labeled initiators such as C-labeled benzoyl peroxide and other related peroxides, and C-labeled AIBN and S-labeled potassium persulfate provide appropriate sensitive methods for determining the number of initiator fragments trapped as end groups in the resulting polymers [10,11]. 

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