Catalyst, ammonium persulfate

We have found that mixing polyacrylamide and starch expands the versatility of both. In our experience, many enzymes that are not well resolved on starch or acrylamide alone are well-resolved on a mixture of the two. The five acrylamide/starch concentrations (weight/volume) we use most often are (1) 12% starch, (2) 7% acrylamide, (3) 9% acrylamide, (4) 7% acrylamide with 2% starch, and (5) 6% acrylamide with 4% starch. For gels containing acrylamide, the total amount of gelling agent is prepared as 95% acrylamide and 5% iV.iV -methylenebisacrylamide. Gel polymerization catalysts, ammonium persulfate (APS) and N,N,N, N -tetxa.-methylethylenediamine (TEMED), are 0.1% (w/v) and 0.2% (v/v) of the total volume of the gel buffer, respectively. 

The most commonly used combination of chemicals to produce a polyacrylamide gel is acrylamide, bis acrylamide, buffer, ammonium persulfate, and tetramethylenediarnine (TEMED). TEMED and ammonium persulfate are catalysts to the polymerization reaction. The TEMED causes the persulfate to produce free radicals, causing polymerization. Because this is a free-radical driven reaction, the mixture of reagents must be degassed before it is used. The mixture polymerizes quickly after TEMED addition, so it should be poured into the gel-casting apparatus as quickly as possible. Once the gel is poured into a prepared form, a comb can be appHed to the top portion of the gel before polymerization occurs. This comb sets small indentations permanently into the top portion of the gel which can be used to load samples. If the comb is used, samples are then typically mixed with a heavier solution, such as glycerol, before the sample is appHed to the gel, to prevent the sample from dispersing into the reservoir buffer. 

There are very few homolytic reactions on triazolopyridines. A suggestion that the ring opening reactions of compound 1 involved free radical intermediates is not substantiated (98T9785). The involvement of radical intermediates in additions to ylides is discussed in Section IV.I. The reaction of radicals with compound 5 and its 1-substituted derivatives gives 4-substituted compounds such as 234 (96ZOK1085). A more detailed study of the reaction of the 1-methyl and 1-phenyl derivatives with r-butanol and ammonium persulfate produced 4-methyl substitution with a silver nitrate catalyst, and the side chain alcohol 235 without the catalyst (96ZOK1412). 

Polymers Polyacrylamide and hydrolyzed polyacrylamide were prepared by the American Cyanamid Company specifically for this project, starting with l C labelled monomer. The radioactivity level of the monomer was kept below 0.20 mC /g in order to avoid significant spontaneous polymerization, utilizing a copper inhibitor. The homopolymer was synthesized by free radical solution polymerization in water at 40°C, using monomer recrystallized from chloroform, an ammonium persulfate-sodium metabisulfite catalyst system, and isopropanol as a chain transfer agent. Sodium... 

Too rapid polymerization can result from high temperatures or too much catalyst. If polymerization is too rapid, the gel may not polymerize evenly, or may polymerize before the gel is completely poured. To prevent these problems, decrease the amount of ammonium persulfate and TEMED by 30%. 

Copolymerization in aqueous emulsion at pH 9-11 with ammonium persulfate as catalyst gave only a low melting wax (mp., 86°C) with a chlorine content of 22.5. ... 

Table I. Heterogeneous Graft Copolymerization of MMA onto Cellulose Using Ammonium Persulfate as a Catalyst...

In an approach to direct C-functionalization of triazolo[4,5-c]pyridines, shown in Scheme 3, 1-methyl (or phenyl)[l,2,3]triazolo[4,5-c]pyridines (26,33) are alkylated exclusively at C-4 by radicals generated by decarboxylation of carboxylic acids (ammonium persulfate-sulfuric acid-silver nitrate) <90ZOB683>. However, with /-butanol various products are obtained depending on the catalyst employed. For example, with ammonium persulfate-sulfuric acid-silver nitrate, exclusive C(4)-methylation (34) was observed, while ammonium persulfate-sulfuric acid gave exclusively C(4)-/ -hydroxy-/ ,/ -dimethylethylation (cf. (36)). The /-butyl analogue (35) was obtained by decarboxylation of pivalic acid. 

Oxidation of arenes (8, 80-81). This oxidation can be carried out in a two-phase system with sodium dodecyl sulfate as a micellar catalyst. CAS can be used in catalytic amounts if ammonium persulfate is used in excess to convert Ce(lll) as formed to Ce(lV). This oxidation is slow in the absence of a Ag(l) salt. This catalytic two-phase oxidation is very useful for preparation of polycyclic quinones from hydrocarbons, but is ineffective for other substrates. 

The usual combination of components in the polymerisation mixture, and the only one for which we shall give experimental details comprises buffer salts acrylamide monomer, methylene N,N -bisacryl-amide (Bis), tetramethyl ethylenediamine (TEMED) as catalyst and ammonium persulfate as initiator. Variants are possible as mentioned in the previous chapter other catalysts may be used and also there may in some cases be advantages in eschewing the use of the persulfate, for example, when it is important to avoid too rapid setting of the gel in the course of more than usually complex... 

Catalyst is added to the mixtures immediately before they are poured into the cell. This comprises 6) TEMED, 40 pi ammonium persulfate, 100 g/1 0.4 ml of this solution is added per 100 ml of acrylamide dilution to provoke polymerisation 7) for acid gels (type 4),... 

PTFE is produced by free-radical polymerization mechanism in an aqueous media via addition polymerization of tetrafluoroethylene in a batch process. The initiator for the polymerization is usually a water-soluble peroxide, such as ammonium persulfate or disuccinic peroxide. A redox catalyst is used for low temperature polymerization. PTFE is produced by suspension (or slurry) polymerization without a surfactant to obtain granular resins or with a perfluori-nated surfactant emulsion polymerization) to produce fine powder and dispersion products. Polymerization temperature and pressure usually range from 0 to 100°C and 0.7 to 3.5 MPa. 

Acrylamide grouts at ambient temperatures are catalyzed with a two-component redox system. One part, the initiator or catalyst, can be a peroxide or a persalt. Ammonium persulfate (AP), a powder, is most commonly used. The second part, the accelerator or activator, is an organic such as triethanolamine, (TEA), nitrilotrispropionamide (NTP), or dimethylaminiopropionitrile (DMAPN). All three have disadvantages. DMAPN, a liquid, is best from a control point of view but is considered a health hazard. NTP, a powder, has limited solubility in water, particularly at low temperatures. TEA, a liquid, is somewhat metal-sensitive. At the present time virtually all U.S. applications use TEA. There are also materials which act as inhibitors and can be used reliably to control gel time. Potassium ferricyanide, KFe, is most often used. 

Riboflavin should be used as catalyst (instead of ammonium persulfate) if enzymes or other macromolecules sensitive to persulfate are to be separated. Riboflavin is also more effective at lower pH than persulfate. The amount of TEMED (N,N,N, N -tetra-methylethylenediamine) should be increased 10-fold for the low pH, discontinuous gel preparations. 

The most widely used chemical oxidants have been ammonium persulfate, (Nn4)2S208, and FeCl3, although hydrogen peroxide and a range of transition metal salts (e.g., Fe3+, Cc4+, Cu2+, Cr6+, andMn7+) have also been employed. The use of H202 (with Fe3+catalyst) is attractive environmentally, as the only by-product is water. For the metal-based oxidants considered by Chao and March,72 infrared (IR) spectroscopy confirmed that similar PPy backbones were formed in each case. 

The free radical initiator may be a redox catalyst such as ammonium persulfate-sodium hydrogen sulfite, a perfluorocarboxylic acid peroxide (RfC00)2, or an azo bis type compound such as azob isisobutylonitrile. 

Polyacrylamide gels with a total acrylamide content of 4-9 per cent T (in per cent) = [acrylamide -I- bismethylene acrylamide]/100) and C = 3-4 per cent (C = [bismethylene acrylamide]/r) are prepared in the standard way using ammonium persulfate as the initiator and tetramethylethylenediamine (TEMED) as the catalyst for gel formation (for general preparation of poly-... 

A double metal oxide sulfate solid superacid (alumina-zirconia/ persulfate, SA-SZ) can be prepared by treatment of a mixture of aluminum hydroxide and zirconium(IV) hydroxide with an aqueous solution of ammonium persulfate, followed by calcination at 650°C. This catalyst can be efficiently utilized in the benzoylation of arenes with benzoyl and parfl-nitrobenzoyl chloride (Table 4.22), giving BPs in interesting yields. Even if 1 g of catalyst is needed for 40 mmol of chloride, the process seems to be quite useful because the catalyst can be readily regenerated by heating after washing with acetone and diethyl ether and reused four times. 

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