Activation of reducing agents. Sodium hydride containing complex reducing agents 29. Epimerization of alcohols by nickel-containing complex reducing agents (NiCRA)

Epimerization of selected alcohols has been easily achieved by nickel-containing Complex Reducing Agents (termed NiCRA) prepared from 2,5-dimethyl-2,5-hexanediol. It is shown that these reactions are under thermodynamic control.     

Activation of reducing agents. Sodium hydride containing complex reducing agents 21. Regioselective reduction of alkene oxides

It is shown that epoxides are reduced by ZnCRA and NiCRA. Interestingly, the simple change in the nature of the metal included in the reagent, changes the regiochemistry of the reduction.     

Activation of reducing agents. Sodium hydride containing complex reducing agents 24. Beneficial effect of Me3SiCl on the reducing properties of NiCRA

Reduction of carbon-carbon double bonds can be achieved with either NiCRA or NiCRASi (nickel containing Complex Reducing Agent activated by Me₃SiCl). Selective reduction of polyunsaturated hydrocarbons or unsaturated ketones are easily performed with both reagents.     

Activation of reducing agents. Sodium hydride containing complex reducing agents 25. A one pot one reagent cross-coupling reaction of aryl halides

The preparation of NiCRA [NaH-AtmONa-Ni(OAc)₂] in the presence of 2,2′-bipyridyl and KI leads to a reagent (termed NiCRA-bpy-KI) which is shown to be one of the most efficient Ni containing reagents reported so far for the cross-coupling of aryl halides.     

Formation of gold nanoparticles using amine reducing agents

We report on the use of amines as reducing agents in the formation of gold nanoparticles. We can predict whether the amines will function as reducing agents in this reaction based on their redox properties. The kinetics of AuNP formation can be understood in terms of Marcus electron transfer theory, where the slower reactions proceed in the inverted region owing to the difference between the Au reduction potential and the amine oxidation potential. For a certain number of the amine reducing agents, following reduction of HAuCl4, a subsequent reaction of the amine radical cation with other reducing agent molecules in solution can form poly(amine)s. These findings point collectively to the utility of amines as reducing agents in AuNP formation and provide information on the conditions under which these reactions will proceed.     

Light production in alkaline mixtures of reducing agents and dimethylbiacridylium nitrate.

Abstract— Kinetic studies were made of light production and 0₂ absorption elicited by treatment of dimethylbiacridylium hydroxide [D(OH)₂] with reducing agents in alkaline aqueous solutions. D(OH)2 addition stimulated O₂ uptake which proceeded with zero-order kinetics until nearly all of the O₂ or of the D(OH)₂ was converted to end products. At the termination of the reactions with fructose as reductant the D(OH)₂ was converted to methylacridone and to dimethylbiacridene each compound accounting for approximately one-half the D(OH)₂ consumed. O₂ was reduced to H₂O₂. With hydroxylamine as the reducing agent the emitted light intensity was related to the first power of the D(OH)₂ concentration and the rate of O₂ uptake to the square root of the D(OH)₂. The disappearance of D(OH)₂ in these circumstances was by a first order or pseudo-first order rate. Fructose as a reducing agent by contrast resulted in an O₂ uptake nearly independent of D(OH)₂ concentration over a range from 1 × 10^-5M-1 × 10^-4M, while the light intensity and disappearance of D(OH)₂ followed a one-half order rate. O₂ uptake was by zero order kinetics and the oxidation of fructose proceeded at the same rate as was found with ferricyanide as oxidant. The kinetics, quantum yields and temperature dependence of the fructose reactions were compared with similar reactions employing H₂O₂ as the light eliciting reagent. The results are interpreted as indicating that D(OH)₂ acts as a chain initiator in a manner analogous to better known, radical producing compounds found to accelerate hydrocarbon autooxidations.     

Solid-phase reducing agents as alternative for reducing disulfide bonds in proteins

Disulfide reduction of Kluyveromyces lactis and Aspergillus oryzae β-galactosidases and β-lactoglobulin was assessed. Reduction was performed using one of two thiol-containing agents: dithiothreitol (DTT) or thiopropyl-agarose with a high degree of substitution (1000 μmol of SH groups/g of dried gel). Both reductants allowed an increase of three- (for K. lactis β-galactosidase) and fourfold (for A. oryzae β-galactosidase) in the initial content of SH groups in the lactases. Nearly sevenfold fewer micromoles of SH groups per milligram of protein were needed to perform the reduction of K. lactis β-galactosidase with thiopropyl-agarose than for the same reduction with DTT. However, for A. oryzae β-galactosidase, nearly twice as many micromoles of SH groups per milligram of protein were needed with thiopropylagarose than with DTT. Disulfide bonds in β-lactoglobulin were not accessible to thiopropyl-agarose, since this reduction was only possible in the presence of 6 M urea. These results proved that highly substituted thiopropyl-agarose is as good a reducing agent as DTT, for the reduction of disulfide bonds in proteins. Moreover, excess reducing agent was very simply separated from the reduced protein by filtration, making it easier to control the reaction and providing reduced protein solutions free of reductant. All these advantages substantially cut down the time required and therefore the cost of the overall process.     

Interaction of cyanocobalamin with sulfur-containing reducing agents in aqueous solutions

The kinetics and mechanism of cyanocobalamin reduction by sodium hydroxymethanesulfinate and dithionite in alkaline media are studied. It is established that the character of the rate-determining step depends on the concentration of the reducing agents: when they are in excess, it is a step of elimination of cyanocobalamin, at lower concentrations of reducing agents a rate-determining is a step of their addition to cobalamin.     

Test determination of reducing agents using noncovalently immobilized quinonimine indicators

The noncovalent immobilization of indophenols (2,6-dichloroindophenol and 2,6-dibromoin-doguaiacol) and indamines (Variamine Blue and Bindshendler’s Green) on reversed-phase silica gels and ion exchangers was studied. It was shown that the properties of indicator powders can be improved by the double modification of reversed-phase silica gels with cetyltrimethylammonium chloride and 2,6-dichloroindophenol or with dodecyl sodium sulfate and Bindshlender’s Green. Ionization constants and formal redox potentials of the noncovalently immobilized quinonimine compounds were determined by solid-phase spectrophotometry. Indicator tubes and indicator powders were proposed for the test determination of 0.3–1000 mg/L ascorbic acid and 0.02–3.0 mg/L iron(II)     

Voltammetric determination of reducing agents and dyestuffs in textile printing pastes

Summary Basic research concerning voltammetry in highly viscous, paste-like systems is presented. Using model compounds for dyestuffs and reducing agents, respectively, the principal applicability of electrochemical techniques for direct quantitative determination of electroactive compounds in such media is proved. The influence of non-Newtonian viscosic properties of the thickeners used (polygalactomannanes, carboxymethylcellulose) on current voltage curves obtained with rotating electrodes is discussed. An increase of the anodic measuring range due to electrode surface modification by the products of the electrode reaction of hydroxymethanesulphinate and by the properties of the thickeners is evaluated.     

Reactivity of alkoxy-NNO-azoxy compounds toward hydrazine hydrate and inorganic reducing agents

The chemical stability of alkoxy-NNO-azoxy compounds to reduction with hydrazine hydrate has been studied. Methoxy-NNO-azoxymethane and bis(methyl-ONN-azoxy) formaldehyde acetal are more stable by orders of magnitude than bis(methoxy-NNO-azoxy)methane and 2,2-bis(methoxy-NNO-azoxy)propane. Methoxy-NNO-azoxymethane is also resistant to reduction with titanium(III) under acidic conditions and with iron(II) under basic conditions. Probable reaction mechanisms have been proposed on the basis of the substrate reactivity toward nucleophiles, acids, and alkalies.