Factors that influence organic acid activity

Factors that influence organic acid activity... 

A key aspect of metal oxides is that they possess multiple functional properties acid-base, electron transfer and transport, chemisorption by a and 7i-bonding of hydrocarbons, O-insertion and H-abstraction, etc. This multi-functionality allows them to catalyze complex selective multistep transformations of hydrocarbons, as well as other catalytic reactions (NO,c conversion, for example). The control of the catalyst multi-functionality requires the ability to control not only the nanostructure, e.g. the nano-scale environment around the active site, " but also the nano-architecture, e.g. the 3D spatial organization of nano-entities. The active site is not the only relevant aspect for catalysis. The local area around the active site orients or assists the coordination of the reactants, and may induce sterical constrains on the transition state, and influences short-range transport (nano-scale level). Therefore, it plays a critical role in determining the reactivity and selectivity in multiple pathways of transformation. In addition, there are indications pointing out that the dynamics of adsorbed species, e.g. their mobility during the catalytic processes which is also an important factor determining the catalytic performances in complex surface reaction, " is influenced by the nanoarchitecture. 

Hepatic Bile Formation. Carrier-mediated active transport of bile acids across the canalicular surface generates osmotic water flow that is a major factor regulating bile formation and secretion. Transport of these organic anions also influences secretion of the remainder of the major components of bile, such as bilirubin, cholesterol, and phospholipids. There is no secretion of the latter two compounds in the absence of bile acid secretion. The influence of bile acid... 

Since the phenoxyalkanoic acid herbicides are degraded in the soil by biological processes, factors that affect microbial activity will directly affect their breakdown. Soil pH, soil type, soil organic matter, herbicide formulation, and herbicide concentration can all influence the rate of microbial decomposition ( 4, 5). Greater effects are experienced with moisture and temperature, since these factors have a profound influence on microbial activity and thus on herbicide breakdown (4 5). It has been concluded ( 5), that soil temperature above 10°C and moistures above the wilting point are necessary for biological degradation of phenoxyalkanoic acids. 

The Michael addition mechanism, whereby sulfur nucleophiles react with organic molecules containing activated unsaturated bonds, is probably a major pathway for organosulfur formation in marine sediments. In reducing sediments, where environmental factors can result in incomplete oxidation of sulfide (e.g. intertidal sediments), bisulfide (HS ) as well as polysulfide ions (S 2 ) are probably the major sulnir nucleophiles. Kinetic studies of reactions of these nucleophiles with simple molecules containing activated unsaturated bonds (acrylic acid, acrylonitrile) indicate that polysulfide ions are more reactive than bisulfide. These results are in agreement with some previous studies (30) as well as frontier molecular orbital considerations. Studies on pH variation indicate that the speciation of reactants influences reaction rates. In seawater medium, which resembles pore water constitution, acrylic acid reacts with HS at a lower rate relative to acrylonitrile because of the reduced electrophilicity of the acrylate ion at seawater pH. 

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