In homogeneous aqueous solution

Decomposition of Hydrogen Peroxide by Catalysts in Homogeneous Aqueous Solution... 

Schwarzenbach RP, R Stierliu, K Lanz, J Zeyer (1990) Quinone and iron porphyrin mediated reduction of nitroaromatic compounds in homogeneous aqueous solution. Environ. Sci. Technol. 24 1566-1574. 

Another intermediate of the photolysis of TiO was observed in experiments with platinized particles (in the absence of polyvinyl alcohol). The spectrum shown in Fig. 22 is prraent immediately after the laser flash. The signal decays as shown by the inset in the figure. The rate of decay is not influenced by oxygen but is increased by oxidizable compounds such as Br ions in the solution. The broad absorption band in Fig. 22 with a maximum at 430 nm was attributed to trapped positive holes. Chemically, a trapped hole is an 0 radical anion. In homogeneous aqueous solution, 0 ... 

The Af-dansylated amino acid (e.g., glycine, leucine, proline) exhibits a yellow fluorescence. The sensitivity of detection for amino acids by this method is about 10 9 mol of amino acid. The advantage of this prodecure in comparison with that using dansyl chloride is the fact that it can be carried out in homogenous aqueous solution without addition of a cosolvent. 191... 

This cycle, often referred to as the Shilov-cycle converts methane into methanol and chloromethane in homogeneous aqueous solution at mild temperatures of 100-120 °C (11). However, while Pt(II) (added to the reaction as PtCl ) serves as the catalyst, the system also requires Pt(IV) (in the form of PtCle-) as a stoichiometric oxidant. Clearly, this system impressively demonstrates functionalization of methane under mild homogeneous conditions, but is impractical due to the high cost of the stoichiometric oxidant used. A recent development by Catalytica Advanced Technology Inc., often referred to as the Catalytica system used platinum(II) complexes as catalysts to convert methane into methyl-bisulfate (12). The stoichiometric oxidant in this case is S03, dissolved in concentrated H2S04 solvent. This cycle is depicted in Scheme 3. 

Schwarzenbach, R. P., R. Stierli, and J. Zeyer (1990), "Quinone and Iron Porphyrine Mediated Reduction of Nitroaromatic Compounds in Homogeneous Aqueous Solution , Env. Sci. Technol. 24/10, 1566-1574. 

Rate data for hydrolysis reactions in homogeneous aqueous solutions have been reviewed (79), but application of these data to environmental conditions involving mineral surfaces remains difficult due to the unknown effects sorption may have. Several studies have demonstrated that acid-catalyzed reactions are promoted if the substrate is sorbed at clay surfaces (70-74 and other works reviewed by Theng, 8), but inhibition may also occur if substrate hydrolysis is base-promoted (74). 

The H+ and NH forms of homoionic montmorillonite promote the hydrolysis of chloro-s-triazines to the hydroxy analogs (hydroxy-s-triazines) (73). Apparently, the surface acidity of these clays was extremely high, since no degradation was observed in control experiments conducted at pH 3.5 in homogeneous aqueous solution. Russell et al. (73) suggested that the hydroxy-s-triazine products were stabilized in the protonated form at the silicate surface. The IR spectra of these surface complexes agreed with the spectra obtained in 6N HC1, and it was inferred that the pH at the clay surface was 3 to 4 units lower than that measured in suspension. 

For a decade or so [CoH(CN)5] was another acclaimed catalyst for the selective hydrogenation of dienes to monoenes [2] and due to the exclusive solubility of this cobalt complex in water the studies were made either in biphasic systems or in homogeneous aqueous solutions using water soluble substrates, such as salts of sorbic add (2,4-hexadienoic acid). In the late nineteen-sixties olefin-metal and alkyl-metal complexes were observed in hydrogenation and hydration reactions of olefins and acetylenes with simple Rii(III)- and Ru(II)-chloride salts in aqueous hydrochloric acid [3,4]. No significance, however, was attributed to the water-solubility of these catalysts, and a new impetus had to come to trigger research specifically into water soluble organometallic catalysts. 

Let us consider now the origin of the effect of varying solvent composition on the hydrogenation rate in diglyme-water mixtures. The key to the explanation comes from the study of the effect of pH on the rate of hydrogenation of maleic and fumaric acids in homogeneous aqueous solutions. Fig. 3.2.a and 3.2.b show these rates as a function of pH together with the concentration distribution of the undissociated (H2A), half dissociated (HA ) and fully dissociated (A ) forms of the substrates [86]. 

E. Szajna-Fuller, Y. L. Huang, J. L. Rapp, G. Chaka, V. S. Y. Lin, M. Pruski, and A. Bakac, Kinetics of oxidation of an organic amine with a Cr(V) salen complex in homogeneous aqueous solution and on the surface of mesoporous silica, Dalton Trans., 17 (2009) 3237-3246. 

Slepnev et al. [313] presented a simple method for protein radio-labeling with Bolten-Hunter reagent (iV-hydroxy succinimide ester of 3-(p-hydroxy di-iodophenyl)) propionic acid) in AOT/octane-RMs using mouse IgG, human transferrin, protein A, and a2-interferon as labeling examples. The yield of radio-labeling in RMs was found to be higher than that achieved in homogeneous aqueous solution. 

Highly strained hydrocarbons such as quadricyclane (structure see below) may serve as high-performance aviation fuels (Hill etal., 1997). It is, therefore, important to know the environmental behavior of such compounds, particularly with respect to spills. In this context, Hill et al. (1997) have studied the hydrolysis of quadricyclane in aqueous solution at pH values between 3 and 4 as well as in soil slurries exhibiting pH values between 4.6 and 6.4. They found that in homogeneous aqueous solution at a given pH, the disappearance of quadricyclane followed pseudo-first-order kinetics, and that two major products (i.e., nortncyclyl alcohol and exo-5-norbomen-2-ol) were formed at a ratio of about 15 ... 

Now we are in the position to rationalize the observations made in Fig. 14.7 by looking at the energetics of the reduction of nitrobenzene to nitrosobenzene by hydrogen sulfide in homogeneous aqueous solution (Fig. 14.9 Ar = C6H5) ... 

Buschmann, J., W. Angst, and R. P. Schwarzenbach, Iron porphyrin and cysteine mediated reduction of ten polyhalogenated methanes in homogeneous aqueous solution Product analyses and mechanistic considerations , Environ. Sci. Technol., 33, 1015-1020 (1999). 

In homogeneous, aqueous solution, alkali metal hydroxides react with carbohydrates to produce negatively charged carbohydrate species. Although the general feeling among chemists is that these species are free alcoholate anions, the possibility that they are composed, at least partially, of carbohydrate-hydroxide ion adducts cannot be dismissed. 

Glod G., Angst W., Holliger C., and Schwarzenbach R. P. (1997) Corrinoid-mediated reduction of tetrachloroethene, trichloroethene, and trichlorofluoroethene in homogeneous aqueous solution reaction kinetics and reaction mechanisms. Environmental Science Technology 31(1), 253-260. 

Lipczynska-Kochany E. Degradation of nitrobenzene and nitrophenols in homogeneous aqueous solution. Direct photolysis versus photolysis in the presence of hydrogen peroxide and the Fenton reagent. Water Pollut Res J Can 1992 27 97-122. 

Murakami et al. utilized catalytic bilayer membranes to catalyze the (1-replacement reaction of serine with indoles [44], The bilayer vesicle formed with 32 and 36 drastically accelerated the (1-replacement reaction by 51-fold (krel) relative to pyridoxal in homogeneous aqueous solution. They attributed this to the hydrophobic microenvironmental effect provided by the bilayer vesicle, which affords effective incorporation of indole molecules and elimination of water molecules in the reaction site. The imida-zolyl group of 33 enhanced the reaction further, krd being 130, possibly due to general acid-base catalysis by the imidazolyl group. Copper(n) ions also improved the reaction. 

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