Carboxylic acids hydrolysis, metal-catalyzed

Quinoline, 2-cyano-8-hydroxy-hydro lysis metal catalysis, 452 Quinoline, 8-hydroxy-carboxylic acid esters hydrolysis, metal-catalyzed, 438 metal complexes... 

By employing anionic techniques, alkyl methacrylate containing block copolymer systems have been synthesized with controlled compositions, predictable molecular weights and narrow molecular weight distributions. Subsequent hydrolysis of the ester functionality to the metal carboxylate or carboxylic acid can be achieved either by potassium superoxide or the acid catalyzed hydrolysis of t-butyl methacrylate blocks. The presence of acid and ion groups has a profound effect on the solution and bulk mechanical behavior of the derived systems. The synthesis and characterization of various substituted styrene and all-acrylic block copolymer precursors with alkyl methacrylates will be discussed. 

Dissolved metals and metal-containing surfaces play an important role in the transformation of organic contaminants in the subsurface environment. Metal ions can catalyze hydrolysis in a way similar to acid catalysis. Organic hydrolyzable compounds susceptible to metal ion catalysis include carboxylic acids, esters, amides, anilides, and phosphate-containing esters. Metal ions and protons... 

Addition of carbon monoxide and water to an alkene, i.e. hydrocarboxylation, is catalyzed by a variety of transition metal complexes, including [Ni(CO)4], [Co2(CO)s] and [HaPtClg]. Unfortunately this reaction usually leads to mixtures of products due to both metal-catalyzed alkene isomerization and the occurrence of Irath Markownikov and anti-Markownikov addition of the metal hydride intermediate to the alkene. The commercially available zirconium hydride [(C5Hs)2Zr(H)Cl] can be used as a stoichiometric reagent for conversion of alkenes to carboxylic acids under mild conditions (equation 23). In this case the reaction with linear alkenes gives exclusively terminal alkyl complexes even if the alkene double bond is internal. Insertion of CO followed by oxidative hydrolysis then leads to linear carboxylic acids in very good yield. 

Adsorption of ionizable organic pollutants onto hydrous metal oxide surfaces in soils, sediments, and aquifers can have an important impact on pathways and rates of chemical transformations. In some instances, a particular degradative pathway can only occur at the oxide/water interface, for example, because of the low solubility of these higher-valent metals in most natural waters. In other instances, the unique chemical microenvironment of the oxide/water interface may catalyze transformations that otherwise would have occurred in solution. Hydrolysis of two carboxylic acid esters catalyzed by hydrous metal oxides is discussed. A detailed understanding of adsorption phenomena provides the basis for assessing the nature and importance of surface chemical transformations. 

The enantioface selective protonation of prochiral enol derivatives is a simple and attractive route for the preparation of optically active carbonyl derivatives. Reports of stoichiometric protonation of metal enolates by a chiral proton source at low temperature leads to optical yields from 20 to 85% ee and yeast esterase catalyzes the hydrolysis of 1-acetoxycycloalkenes with enantioselectivi-ties between 41 and 96% for enol protonation [17,18]. These reactions involve enolates under basic conditions. Hydrolysis of enol ethers under acidic conditions proceeds via a rate-determining carbon protonation and is catalyzed by carboxylic acids [19,20]. Raymond et al. [21] reasoned that a complementary... 

The reactions of metallated 2-methyloxazolines with carbonyl compounds to provide adducts constitute the key step in a general procedure for the conversion of carbonyl compounds into 0-hydroxy carboxylic acids and esters or their a,0-unsaturated counterparts (Schemes 21-26)44-50 For example, reaction of the lithiated derivative of (54) with carbonyl compounds provides the adducts (55) in high yield (Scheme 21). Subsequent acid-catalyzed hydrolysis provides the unsaturated carboxylic acids (56) depending upon the severity of the reaction conditions, acid-induced ethanolysis can be performed on the adducts (55) to provide either the unsaturated esters (57) or the 0-hydroxy esters (58) in good yields (Table 7).4S The main limitation of the method is that extensive retroaldolization occurs upon attempts to hydrolyze adducts (55 R1 = alkyl), so a-alkyl-0-hydroxy esters and acids do not appear to be accessible. 

Hydrolysis of carboxylic and phosphoric esters is also a slow process at neutral pH, and is catalyzed by acids and bases by mechanisms similar to those involved in amide and peptide hydrolysis. Metal ions are also good catalysts of both carboxylic and phosphoric ester hydrolysis, typically with rate increases much higher than those observed for hydrolysis of amides or peptides (Table... 

Again by analogy with peptide hydrolysis, metalloenzymes catalyzing ester hydrolysis may take advantage of additional chemical features provided by amino-acid residues present in the active-site cavity. This situation occurs with car-boxypeptidase, " which shows esterase activity in vitro. Although the rate-limiting steps for carboxylic esters and peptides may differ, several features, such as the pH dependences of cat and and the presence of two spectroscopically observable intermediates, point to substantially similar mechanisms. On the other hand, carboxylic ester hydrolysis catalyzed by carbonic anhydrase seems to rely on fewer additional features of the active-site cavity, perhaps only on the presence of a metal-coordinated hydroxide that can perform the nucleophilic attack on the carbonyl carbon atom." ... 

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