Initiators bisulfite

Poly(acrylamide) and its acrylic acid copolymers were obtained from polymerization of the monomers in aqueous solution using ammonium persulfate/sodium bisulfite initiator following the procedure reported by Fong and Kowalski.5 Depending on the amount of initiator used, the average molecular weights of the polymers were between 6,000 to 50,000 as determined by gel permeation chromatography (GPC). Taurine (2-aminoethanesulfonic acid) and sodium formaldehyde bisulfite were purchased from Aldrich and used without purification. 

Persulfate-bisulfite-initiated graft polymerization was accomplished (Table I) using the procedure of Feairheller et al (11). Lyophilized rat skins were soaked in 100 ml of a 0.4% aqueous solution of an octyl-phenyl ether of polyethylene glycol containing 9-10 ethylene oxide groups. After 1 hr, 0.4 g potassium persulfate and 0.135 g sodium bisulfite were added, and CO2 was passed through the solution before 5 ml of monomer were added. 

Polymerization of phenyl or cyclohexyl methacrylate in 2,6-dimethyl-/3-cyclodextrin in water using a potassium persulfate-potassium bisulfite initiator gave better yields and higher molecular weights than obtained with an azo initiator in tetrahydrofuran.234... 

TABLE III Emulsion Polymerization of Dithioacids and Biallyl Persulfate-Bisulfite Initiated"... 

In certain cases extremely high sensitivity may be attained with radioactive labeling (30). Using radiolabeled ( S) bisulfite initiator, the nnmber-average molecular weight of Teflon samples was determined in the range of 389,000-8,900,000 (31). This is a particularly useful technique for insoluble pol5uners. 

Other solvents and initiators are, for example, butanone [495] or ethyl methyl ketone [470,476] with AIBN [496-499] and dioxane with benzoyl peroxide [474,484,500,503]. In benzene as solvent the resulting polymer forms a slurry [504]. AIBN can be used as an initiator in aqueous solutions by solubilizing the initiator with 4% ethanol [504]. Methacrylic acid polymerizes in nitric acid at 5 to 30 °C to a molar mass of 2 x 10 and the product precipitates in acetone as a white powder [505]. Nitrogen dioxide reacts as an initiator in benzene to synthesize poly(acrylic acid) at 50 °C with molar masses of 48,000 [506]. Sodium bisulfite initiates polymerization of methacrylic acid in an aqueous medium but is ineffective for acrylic acid [507]. 

Bisulfite Initiator - This is a redox initiator for dispersion polymerization of tetrafluoroethylene. For example, sodium bisulfite is a redox initiator from the bisulfite family and may be combined with ferrictriphosphate (activator) for polymerization. 

In a typical adiabatic polymerization, approximately 20 wt % aqueous acrylamide is charged into a stainless steel reactor equipped with agitation, condenser, and cooling jacket or coils. To initiate the polymerization, an aqueous solution of sodium bisulfite [7631-90-5] is added, followed by the addition of a solution of ammonium persulfate [7727-54-0] N2HgS20g. As the polymerization proceeds, the temperature rises to about 90°C, and then begins to fall at the end of the polymerization. The molecular weight obtained depends primarily on the initiator concentration employed. 

Isothermal polymerizations are carried out in thin films so that heat removal is efficient. In a typical isothermal polymerization, aqueous acrylamide is sparged with nitrogen for 1 h at 25°C and EDTA (C2QH2 N20g) is then added to complex the copper inhibitor. Polymerization can then be initiated as above with the ammonium persulfate—sodium bisulfite redox couple. The batch temperature is allowed to rise slowly to 40°C and is then cooled to maintain the temperature at 40°C. The polymerization is complete after several hours, at which time additional sodium bisulfite is added to reduce residual acrylamide. 

The reversible addition of sodium bisulfite to carbonyl groups is used ia the purification of aldehydes. Sodium bisulfite also is employed ia polymer and synthetic fiber manufacture ia several ways. In free-radical polymerization of vinyl and diene monomers, sodium bisulfite or metabisulfite is frequentiy used as the reduciag component of a so-called redox initiator (see Initiators). Sodium bisulfite is also used as a color preventative and is added as such during the coagulation of crepe mbber. 

Both 1- and 2-naphthylhydrazine have been shown to react in good yield with 2-hydroxy-3-naphthoic acid in the presence of sodium bisulfite to give, after acidic workup, dibenzocarbazole 30 and 31, respectively7 When either 1- or 2-naphthylhydrazine is heated with sodium bisulfite, dibenzocarbazoles 32 and 31, respectively, are isolated after acidic work-up7 It is suggested that loss of the hydrazine residue to form a bisulfite addition compound of the parent naphthol occurs initially further reaction of this adduct with naphthylhydrazine then affords, after work-up, the products. 

Naphthol 1 is initially protonated at a carbon center of high electron density (C-2 or C-4). The cationic species 3 thus formed is stabilized by resonance it can add a bisulfite anion at C-3. The addition product can tautomerize to give the more stable tetralone sulfonate 4 the tetralone carbonyl group is then attacked by a nucleophilic amine (e.g. ammonia). Subsequent dehydration leads to the cation... 

Reduction by sodium dithionite. A small amount of sodium dithionite, solid or in solution, is added to a luciferase solution made with 50 mM phosphate, pH 7.0, containing 50 pM FMN. The amount of dithionite used should be minimal but sufficient to remove oxygen in the solution and to fully reduce the flavin. The solution made is injected into an air-equilibrated buffer solution containing a long-chain aldehyde and luciferase to initiate the luminescence reaction. With this method, the reaction mixture will be contaminated by bisulfite and bisulfate ions derived from dithionite. 

Persulfate (41) reacts with transition metal ions (e.g. Ag, Fe21, Ti31) according to Scheme 3.42. Various other reduetants have been described. These include halide ions, thiols (e.g. 2-mercaptoethanol, thioglycolic acid, cysteine, thiourea), bisulfite, thiosulfate, amines (triethanolamine, tetramethylethylenediamine, hydrazine hydrate), ascorbic acid, and solvated electrons (e.g. in radiolysis). The mechanisms and the initiating species produced have not been fully elucidated for... 

Initially, 50 was converted into the benzoxazinone 51 by reaction with phosgene in the presence of triethylamine and 51 was isolated in 95% yield upon crystallization from methanol. Deprotection of the pMB group from 51 was accomplished with ceric ammonium nitrate (CAN) in aqueous acetonitrile. Efavirenz was isolated in 76% yield after crystallization from EtOAc-heptane (5 95), as shown in Scheme 1.19. There were two issues identified in this route. First, lequiv of ani-saldehyde was generated in this reaction, which could not be cleanly rejected from product 1 by simple crystallization to an acceptable level under the ICH guideline. Anisaldehyde was removed from the organic extract as a bisulfite adduct by washing with aqueous Na2S205 twice, prior to the crystallization of 1. Secondly,... 

The living radical polymerization process is also valid for the polymerization of water-soluble monomers. The polymerization of sodium styrenesulfonate in aqueous ethylene glycol (80%) in the presence of TEMPO using potassium per-sulfate/sodium bisulfite as the initiator at 125 °C gave a water-soluble polymer with well-controlled molecular weight and its distribution [207]. 

All reactions were stirred at speeds in excess of 500 rpm to eliminate any effects due to stirring rate (17). Initially, polymerizations were conducted at 60 C in cyclohexanone solution. When 18-crown-6 was used as the catalyst, little difference was observed in the presence or absence of sodium bisulfite. 

For QM-MSP, first the promoter regions of several genes will be amplified using primes that correspond to the CG-free regions (45). Then, 1 pL of the diluted PCR product (30-50 times) is used as the template in real-time QM-MSP to quantify the methylated and unmethylated template in separate reactions using methylation- or nonmethylation-specific primers. The benefits of this method are that (1) the instability of bisulfite-modified DNA is remedied using an initial round of PCR (2) nonspecific products that compromise the accuracy of SYBR green-based real-time PCR are eliminated in the second-round PCR (3) the likelihood of the development of primer dimers is minimized as the first-round PCR product is diluted 50 times and a minimal amount of MSP primers is used in the second-round PCR (4) the amount of the precious DNA used in this approach is substantially less than in the other methods. 

The initiators used in emulsion polymerization are water-soluble initiators such as potassium or ammonium persulfate, hydrogen peroxide, and 2,2 -azobis(2-amidinopropane) dihydrochloride. Partially water-soluble peroxides such a succinic acid peroxide and f-butyl hydroperoxide and azo compounds such as 4,4 -azobis(4-cyanopentanoic acid) have also been used. Redox systems such as persulfate with ferrous ion (Eq. 3-38a) are commonly used. Redox systems are advantageous in yielding desirable initiation rates at temperatures below 50°C. Other useful redox systems include cumyl hydroperoxide or hydrogen peroxide with ferrous, sulfite, or bisulfite ion. 

Synthesis from a-Pinene. a-Pinene from turpentine oil is selectively hydrogenated to cis-pinane [35], which is oxidized with oxygen in the presence of a radical initiator to give a mixture of ca. 75% cis- and 25% tran -pinane hydroperoxide. The mixture is reduced to the corresponding pinanols either with sodium bisulfite (NaHS03) or a catalyst. The pinanols can be separated by... 

In the polymerization of acrylic monomers by bulk, suspension, or in organic solution, the most common initiators are diacyl peroxide (e.g., dibenzoyl peroxide supplied as a paste in water) or azo compounds (e.g., 2,2 -azobisisobutyronitrile). For emulsion or aqueous solution polymerizations, sodium persulfate by itself or in combination with bisulfites or a host of other reducing agents may be used. 

More definite evidence for the transient existence of the un-cyclized l-(jS-aminoethyl)-3,4-benzoquinones has been obtained recently by Kodja and Bouchilloux,77 78 who noted that a transient yellow color (Amax ca. 385 mp) was occasionally observed during the enzymic oxidations of catecholamines (particularly in unbuffered systems at low temperatures). This phenomenon was probably due to the formation of the transient o-quinones. (The absorption maximum of o-benzoquinone, the effective chromophore of the open-chain quinones, is known to occur at ca. 390 mp.79) An absorption maximum at 390 mp is characteristic of the formation of the dopa-quinone chromophore during oxidation of small C -terminal tyrosine peptides in the presence of tyrosinase.37 48 Similar spectroscopic features were observed when the oxidations were carried out with lead dioxide in sulfuric acid solutions (pH> 1). If the initial oxidation was carried out for a short period of time, it was possible to regenerate the original catecholamines by reduction (e.g. with sodium bisulfite, potassium iodide, and zinc powder) and to show that the 385 mp peak disappeared.77,78 Kodja and Bouchilloux were also able to identify 2,4-dinitrophenylhydrazones of several of the intermediate non-cyclized quinones by paper chromatography and spectroscopy (Amax n weakly acid solution ca. 350 mp with a shoulder at ca. 410 mp).77,78... 

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