Poly reducing agent

Poly(hydrosilane)s have been used as radical-based reducing agents for organic halides (RX, where X = Cl, Br, 1), rivaling the effectiveness of the (TMSlsSiH. A rate constant (fcn referring to each SiH moiety) in the range of (5-60) xlO M s is estimated for the reaction of primary alkyl radicals with 123. ... 

Hydrolysis increases the terpolymer limiting viscosity number in water by a factor of up to 45. Other previously published data(66-68) show that these terpolymers are nonnewtonian viscosifiers, metal-ion complexing agents, and effective flocculators. These materials are still "small" molecules in aqueous solution, however, and do not function as effectively when used 1. as nonnewtonian viscosifiers or 2. drag reducing agents as do poly(l-amidoethylene-co-(sodium 1-carboxylatoethylene)) copolymers. 

Most poly(HA) depolymerases are inhibited by reducing agents, e.g., dithio-erythritol (DTT), which indicates the presence of essential disulfide bonds, and by serine hydrolase inhibitors such as diisopropyl-fluoryl phosphate (DFP) or acylsulfonyl derivates. The latter compounds covalently bind to the active site serine of serine hydrolases and irreversibly inhibit enzyme activity [48]. 

Polyethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) (Pluronic) block copolymer is a very efficient reducing agent and nanoparticle stabilizer. Au NPs of about 10 nm can be stabilized with PEO-PPO-PEO block copolymer solutions in water and at room temperature and using HAuC14 as precursor. The formation of gold nanoparticles is controlled by the overall molecular weight and relative block length of the block copolymer [118]. 

Poly-p-xylylenes were prepared in excellent yield by electrolytic reduction of a,a -dihalo-/>-xylenes at controlled cathode potentials (28). Polymer and halides are formed at the cathode at the anode the halide is oxidized to halogen. It has been known that some of the a-a -dihalo- -xylene type of compounds have been polymerized by a variety of reducing agents, such as zinc, copper, phenyllithium, sodium and iron ... 

In the same study, redox polymers (223) were prepared that contained pendant viologens (Scheme 108). An active reducing agent was obtained by chemical reduction with dithionite or zinc, electrochemically, or by exposure to light. Utilization of the reduced poly(viologen) (224) as an electron transfer mediator was demonstrated by addition of a catalytic amount of the polymer to a mixture of zinc powder, ethyl benzoylformate (225) and water-acetonitrile (1 5). A quantitative yield of ethyl mandelate (226) was obtained after two days at room temperature (Scheme 109). Without the polymer, no reaction was observed after a month. 

Polyacrylamides are chemically stable towards acids (TFA, hydrogen fluoride [163]), bases, and weak oxidants or reducing agents. Problems, which might be related to cleavage of the amide bonds in poly(7V,/V-dialkylacrylamidcs), were encountered upon treatment of such supports with sodium in liquid ammonia [169]. 

In its solutions in liquid NIL. cesium is like the other alkali metals, a powerful reducing agent, so that in such solutions, titrations of cesium poly sulfide with cesium are made by eleclrumeiric methods. The solubility of cesium salts in liquid NHi increases markedly with the radius of an anion (the chloride. CsCI. 0.0227 moles per kg. the bromide. CsBr, 0.215 moles per kg. and the iodide. Csl. 5.84 moles per kg), though the values are less than for the corresponding rubidium compounds. 

Mono- or poly-substitnted nitro-compounds are changed in whole or in part to the corresponding amino-compounds by proper choice of reducing agent and temperature, e.g., in acid medium 1,3-dinrtrobenzene yields 1,3-phenylenediamine, C6H4(NH2)2( 1. 3), and with ammonium suliide yields 3-nitroaniline (1 )H C,H, NO,(3). When diphenylnitrosamine is reduced, 1,1-diphenylhydrazine, (CbH,)2N NH>. is formed. 

It is interesting to conclude this section with an example that, in a sense, brings the chapter full circle. The metallization of plastic materials used as metal substitutes is a process with actual and future commercial potential. Usually, plastics are plated after appropriate sensitization by an electroless process which involves reduction of metal ions (e.g. Ni2+, Cu2+) by chemical rather than electrical means.19 There seems no reason why the reducing agent should not be incorporated in the polymer and Murray and his collaborators101 have demonstrated that copper, silver, cobalt and nickel may each be electrodeposited on to films of [poly-Ru(bipy)2(4-vinylpyridine)2]2+ coated on to platinum electrodes. The metal reductions are mediated by the Ru1 and Ru° states of the polymer. 

This formula requires only one-fourth of the reducing agent usually needed. In the case of poly sulfide melt dyes, the reducing agent can act not just on the disulfide groups but also on the quinoneimine group (as in vat dyes). 

Compounds with a terminal acetylenic function, RCsCH, react with 1-bromoalkynes, R CsCBr in the presence of an aliphatic amine and a catalytic amount of a copper salt to give the coupling products RCsCCsCR. This useful reaction, discovered by Cadiot and Chodkiewicz [195], gives a ready access to a number of poly-unsaturated systems. The usual procedure involves dropwise addition of the bromoacetylene R GsCBr to a mixture of the acetylene RCsCH, ethylamine, ethanol or methanol, a catalytic amount of copper chloride or bromide and a small amount of hydroxylamine.HCl. This reducing agent prevents the oxidation to copper ). The reaction is usually very fast at temperatures in the region of 30 C. Since much heat is evolved, the reaction can be monitored easily by temperature observation. 

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