Kinetics reduction

The contrasting regiochemistry of hydroboration for 1-chloroalkynes and 1-chloroalkenes is explained that the +M effect [3], in the chloroalkyne is a small one relative to the stronger charge pattern of the alkyne moiety, which places more electron density at the 1 position. 

The steric and electronic effects of halogen substituents bring about dramatic rate decrease in the order Cl Br I, the trend one expects if the induction by 

The kinetic reduction of a number of aldehydes and ketones with (9-BBN)2 is studied at 25 °C. The reduction of aldehydes and reactive ketones follows first-order kinetics (Table 4.17) [1], thus supporting the dissociation mechanism. 

In THF solvent, a much larger first-order rate constant, similar to hydrobora-tion [2], is observed. This solvent effect is attributed [2] to the direct attack of the THF molecule on (9-BBN)j, which breaks the B-H bridge bond [3] (Table 4.17) [1]. 

As in the case of hydroboration, the reduction rate of sterically hindered ketones such as 2,4-dimethyl-3-pentanone is considerably slower and exhibits three-halves-order kinetics, first order in ketone, and one-half order in (9-BBN)j. 

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Alkaline Fuel Cell. The electrolyte ia the alkaline fuel cell is concentrated (85 wt %) KOH ia fuel cells that operate at high (- 250° C) temperature, or less concentrated (35—50 wt %) KOH for lower (<120° C) temperature operation. The electrolyte is retained ia a matrix of asbestos (qv) or other metal oxide, and a wide range of electrocatalysts can be used, eg, Ni, Ag, metal oxides, spiaels, and noble metals. Oxygen reduction kinetics are more rapid ia alkaline electrolytes than ia acid electrolytes, and the use of non-noble metal electrocatalysts ia AFCs is feasible. However, a significant disadvantage of AFCs is that alkaline electrolytes, ie, NaOH, KOH, do not reject CO2. Consequentiy, as of this writing, AFCs are restricted to specialized apphcations where C02-free H2 and O2 are utilized. 

The optical absorption spectra of Pu ions in aqueous solution show sharp bands in the wavelength region 400—1100 nm (Fig. 4). The maxima of some of these bands can be used to determine the concentration of Pu ions in each oxidation state (III—VI), thus quantitative deterrninations of oxidation—reduction equiUbria and kinetics are possible. A comprehensive summary of kinetic data of oxidation—reduction reactions is available (101) as are the reduction kinetics of Pu + (aq) (84). 

Ellipsometry (kinetics) Electrometric reduction (kinetics thickness) Interference colours and spectrophotometry (kinetics thickness)... 

The NO reduction over Cu-Ni-Fe alloys has been studied recently by Lamb and Tollefson. They tested copper wires, stainless steel turnings, and metal alloys from 378 to 500°C, at space velocities of 42,000-54,000 hr-1. The kinetics is found to be first order with respect to hydrogen between 400 and 55,000 ppm, and zero order with respect to NO between 600 and 6800 ppm 104). The activation energies of these reactions are found to be 12.0-18.2 kcal/mole. Hydrogen will reduce both oxygen and NO when they are simultaneously present. CO reduction kinetics were also studied over monel metals by Lunt et al. 43) and by Fedor et al. 105). Lunt speculated that the mechanism begins by oxidant attack on the metal surface... 

The first reductive kinetic resolution of racemic sulphoxides was reported by Balenovic and Bregant. They found that L-cysteine reacted with racemic sulphoxides to produce a mixture of L-cystine, sulphide and non-reduced optically active starting sulphoxide (equation 147). Mikojajczyk and Para reported that the reaction of optically active phosphonothioic acid 268 with racemic sulphoxides used in a 1 2 ratio gave the non-reduced optically active sulphoxides, however, with a low optical purity (equation 148). It is interesting to note that a clear relationship was found between the chirality of the reducing P-thioacid 268 and the recovered sulphoxide. Partial asymmetric reduction of racemic sulphoxides also occurs when a complex of LiAlH with chiral alcohols , as well as a mixture of formamidine sulphinic acid with chiral amines, are used as chiral reducing systems. ... 

Zhang J, Vukmirovic MB, Sasaki K, Nilekar AU, Mavrikakis M, Adzic RR. 2005a. Mixed-metal Pt monolayer electrocatalysts for enhanced oxygen reduction kinetics. J Am Chem Soc 127 12480-12481. 

There are several factors through which anions can influence the pathway and O2 reduction kinetics. The main factors are competition with O2 for surface sites changes in the activity coefficients of the reactants, intermediates, and transition states and the acidity and dielectric properties of the electrolyte side of the interface [Adzic, 1998]. For example, perfluoro acids have higher O2 solubility and lower adsorbability than... 

Murthi VS, Urian RC, Mukeijee S. 2004. Oxygen reduction kinetics in low and medium temperature acid environment Correlation of water activation and surface properties in supported Pt and Pt alloy electrocatalysts. J Phys Chem B 108 11011-11023. 

Hsueh KL, Gonzalez ER, Srinivasan S. 1983. Electrolyte effects on oxygen reduction kinetics at platinum—A rotating-ring disk electrode analysis. Electrochim Acta 28 691-697. 

Komanicky V, Menzel A, You H. 2005. Investigation of oxygen reduction kinetics at (111)-(100) nanofaceted platinum surfaces in acidic media. J Phys Chem B 109 23550-23557. 

Abstract A review is provided on the contribution of modern surface-science studies to the understanding of the kinetics of DeNOx catalytic processes. A brief overview of the knowledge available on the adsorption of the nitrogen oxide reactants, with specific emphasis on NO, is provided first. A presentation of the measurements of NO, reduction kinetics carried out on well-characterized model system and on their implications on practical catalytic processes follows. Focus is placed on isothermal measurements using either molecular beams or atmospheric pressure environments. That discussion is then complemented with a review of the published research on the identification of the key reaction intermediates and on the determination of the nature of the active sites under realistic conditions. The link between surface-science studies and molecular computational modeling such as DFT calculations, and, more generally, the relevance of the studies performed under ultra-high vacuum to more realistic conditions, is also discussed. 

Angelova B, Avramova T, Stefanova L, Mutafov S (2008) Temperature effect of bacterial azo bond reduction kinetics an Arrhenius plot analysis. Biodegradation 19(3) 387-393... 

M. J. L. Gines and C. R. Apesteguia, Water-gas shift Reaction reduction kinetics and mechanism of CuZnO/Al203 catalysts, 2001. 

Bhattacharyya, A.K., Lipka, J.J., Waskell, L. and Tollin, G. (1991) Laser flash photolysis studies of the reduction kinetics of NADPH cytochrome P-450 reductase. Biochemistry, 30 (3), 759-765. 

White, A. F., and A. Yee (1985), "Aqueous Oxidation-Reduction Kinetics Associated with Coupled Electroncation Transfer from Iron-containing Silicates at 25° C", Geochim. Cosmochim. Acta 49, 1263-1275. 

The electroreduction of some typically inorganic compoimds such as nitrogen oxides is catalysed by the presence of polymeric osmium complexes such as [Os(bipy)2(PVP)2oCl]Cl, where bipy denotes 2,2 -bipyridyl and PVP poly(4-vinylpyridine). This polymer modifies the reduction kinetics of nitrite relative to the reaction at a bare carbon electrode, and provides calibration graphs of slope 0.197 nA with detection limits of 0.1 pg/mL and excellent short-term reproducibility (RSD = 2.15% for n = 20). The sensor performance was found to scarcely change after 3 weeks of use in a flow system into which 240 standards and 30 meat extracts were injected [195]. 

Effect of dynamical solvent property on the reduction kinetics... 

For evaluating the reduction kinetics of NACs in a given natural system, the relative reaction rates of a series of NACs with known E]u(ArN02) values can be used to... 

Agrawal and Tratnyek (1996) have investigated the reduction of a series of NACs spanning a wide range of (ArN02) values by zero-valent iron metal grains in batch reactors. The observed reduction kinetics were first order, and virtually... 

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