Oxidations of acetals

The oxidation of acetic acid is difficult to accomplish. It does not react in solutions of KjCrjOj or KMn04. Vigorous treatment, such as burning,... 

The addition of various Kolbe radicals generated from acetic acid, monochloro-acetic acid, trichloroacetic acid, oxalic acid, methyl adipate and methyl glutarate to acceptors such as ethylene, propylene, fluoroolefins and dimethyl maleate is reported in ref. [213]. Also the influence of reaction conditions (current density, olefin-type, olefin concentration) on the product yield and product ratios is individually discussed therein. The mechanism of the addition to ethylene is deduced from the results of adsorption and rotating ring disc studies. The findings demonstrate that the Kolbe radicals react in the surface layer with adsorbed ethylene [229]. In the oxidation of acetate in the presence of 1-octene at platinum and graphite anodes, products that originate from intermediate radicals and cations are observed [230]. 

The photo-Kolbe reaction is the decarboxylation of carboxylic acids at tow voltage under irradiation at semiconductor anodes (TiO ), that are partially doped with metals, e.g. platinum [343, 344]. On semiconductor powders the dominant product is a hydrocarbon by substitution of the carboxylate group for hydrogen (Eq. 41), whereas on an n-TiOj single crystal in the oxidation of acetic acid the formation of ethane besides methane could be observed [345, 346]. Dependent on the kind of semiconductor, the adsorbed metal, and the pH of the solution the extent of alkyl coupling versus reduction to the hydrocarbon can be controlled to some extent [346]. The intermediacy of alkyl radicals has been demonstrated by ESR-spectroscopy [347], that of the alkyl anion by deuterium incorporation [344]. With vicinal diacids the mono- or bisdecarboxylation can be controlled by the light flux [348]. Adipic acid yielded butane [349] with levulinic acid the products of decarboxylation, methyl ethyl-... 

Although catalytic wet oxidation of acetic acid, phenol, and p-coumaric acid has been reported for Co-Bi composites and CoOx-based mixed metal oxides [3-5], we could find no studies of the wet oxidation of CHCs over supported CoO catalysts. Therefore, this study was conducted to see if such catalysts are available for wet oxidation of trichloroethylene (TCE) as a model CHC in a continuous flow fixal-bed reactor that requires no subsequent separation process. The supported CoOx catalysts were characterized to explain unsteady-state behavior in activity for a certain hour on stream. 

Kinetics for Ce(IV) perchlorate oxidation of acetic acid in HCIO4 media at 50-60 °C approximate to first-order in both oxidant and substrate and a plot ot versus is linear. A complex was identified 286 nm) and... 

A slow oxidation of acetic acid by Mn(III) acetate occurs at 100 °C to give mainly acetoxyacetic acid and CO2 with an activation energy of 28 kcal.mole F In the presence of excess Mn(Il) a first-order disappearance of oxidant is found . The low yield of methane is incompatible with an initial homolysis of the type... 

The oxidation of acetate under anaerobic conditions can take place by different pathways, both of which have been investigated in detail and their enzymology delineated (Thauer et al. 1989). 

The anaerobic degradation of halogenated alkanoic acids has, however, been much less exhaustively examined. Geobacter (Trichlorobacter) thiogenes was able to transform trichloroacetate to dichloroacetate by coupling the oxidation of acetate to CO2 with the reduction of sulfur to sulfide that carries out the dechlorination (De Wever et al. 2000). 

A facultatively anaerobic organism designated Anaeromyxobacter dehalogenans (Sanford et al. 2002) was capable of dechlorinating ortho-chlorinated phenols using acetate as electron donor—2-chlorophenol was reduced to phenol and 2,6-dichlorophenol to 2-chloro-phenol (Cole et al. 1994). A strain of Desulfovibrio dechloracetivorans was also able to couple the dechlorination of ortho-substituted chlorophenols to the oxidation of acetate, fumarate, lactate, and propionate (Sun et al. 2000). 

Sun B, JR Cole, RA Sanford, JM Tiedje (2000) Isolation and characterization of Desulfobvibrio dechlorace-tivorans sp. nov., a marine dechlorinating hacterium growing hy coupling the oxidation of acetate to the reductive dechlorination of 2-chlorophenol. Appl Environ Microbiol 66 2408-2413. 

Peracetic acid is produced in equilibrium with acetic acid by the reaction of acetic anhydride with hydrogen peroxide, as in Scheme 10.37. Alternatively, peracetic acid can be produced by acid-catalysed oxidation of acetic acid with hydrogen peroxide, as in Scheme... 

Admixture causes explosion, owing either to direct oxidation of acetic acid by the highly concentrated hydrogen peroxide produced, or perhaps to formation of concentrated peroxyacetic acid. 

By oxidation of acet-/>-toluidide, followed by esterification of the 7>-aminobenzoic acid. Chemnitius, Pharm. Zentralh. 68, 765 (1927). 

Among the preferred and also first oxidants to be used for this purpose was manganese(III) acetate in acetic acid, for which the formula Mn30(0Ac)7 might be appropriate53,87. Oxidation of acetic acid, for example, leads to radical 54 which, upon addition to butadiene and oxidation of the adduct radical, leads to /-lactone 55 (equation 24). 

The oxidation of acetate by baker s yeast is 95 per cent inhibited by 0 001 M fluoroacetate,4 but not by chloroacetate, iodoacetate, fluorobutyrate and fluorocrotonate. 

Cause of fluoroacetate poisoning In 1947 Bartlett and Barron,1 using tissue slice, showed that fluoroacetate blocked the oxidation of acetate competitively, and that this accounted for the toxic effect, namely, the body was deprived of acetate. Liebig and Peters then found that fluoroacetate blocked the oxidation of fumarate in a guinea-pig s kidney homogenate without accumulation of acetate hence Bartlett and Barron s hypothesis could not be the whole story. 

In the addition to nonactivated alkenes, where the direct anodic oxidation is less, satisfactorily good yields can be achieved when Mn(OAc)2 is used as mediator (Table 8, entries 6, 7). Sorbic acid precursors have been obtained in larger scale and high current efficiency by a Mn(III)-mediated oxidation of acetic acid/acetic anhydride in the presence of butadiene [112]. 

Galushko AS, Schink B. 2000. Oxidation of acetate through reaction of the citric acid cycle by Geobacter sulfurreducens in pure culture and in syntrophic coculture. Arch Microbiol 174 314-21. 

Transition into the Kolbe region at platinum is associated with the formation of an oxide layer. Acetate ions are believed to be more strongly adsorbed on this layer than is water. Conversion of water to oxygen is then suppressed in favour of the oxidation of acetate ions [59, 60. Electron transfer from acetate is synchronous with cleavage of the alkyl-carboxylate bond leaving adsorbed carbon dioxide and... 

An interpretation of the oxidation of acetals by chromium trioxide is summarized in Scheme 1 the reagent could initially remove a proton from the acetalic carbon atom, to give a dioxolan-(or dioxan-)2-ylium ion, rapidly hydrolyzed to an ester (formyl, acetyl, or benzoyl) of an a-alcohol, which would be further oxidized to a ketone [see Scheme 1, path (a)] in the case of methylene acetals, in the presence of acetic anhydride (which acts as a water scavenger), the intermediate is further oxidized, probably through a chromic ester. 

The eight-step cyclic process for oxidation of simple two-carbon acetyl groups to C02 may seem unnecessarily cumbersome and not in keeping with the biological principle of maximum economy. The role of the citric acid cycle is not confined to the oxidation of acetate, however. 

The common ion effect must also be considered, since it affects each one of the crystallization equilibrium, both in supercritical and subcritical water. Adding sodium acetate, for instance, to a solution containing sodium salts would favour sodium bicarbonate precipitation (formed from oxidation of acetate), thus avoiding the precipitation of more corrosive salts, such as the chloride or sulfate [28],... 

One of the first persons to study the oxidation of organic compounds by animal tissues was T. Thunberg, who between 1911 and 1920 discovered about 40 organic compounds that could be oxidized by animal tissues. Salts of succinate, fumarate, malate, and citrate were oxidized the fastest. Well aware of Knoop s (3 oxidation theory, Thunberg proposed a cyclic mechanism for oxidation of acetate. Two molecules of this two-carbon compound were supposed to condense (with reduction) to succinate, which was then oxidized as in the citric acid cycle to oxaloacetate. The latter was decarboxylated to pyruvate, which was oxidatively decarboxylated to acetate to complete the cycle. One of the reactions essential for this cycle could not be verified experimentally. It is left to the reader to recognize which one. 

It may be noted that l,2,3,4-tetra-0-benzoyl-5,6-0-isopropylidene-D-glucitol (52) has been oxidized with trityl tetrafluoroborate324 325 to 3,4,5,6-tetra-O-benzoyl-keto-L-sorbose (53) in 50% yield. This illustrates an interesting oxidation of acetals, and constitutes a partial, chemical synthesis of L-sorbose (25) from D-glucitol (24). 

Other reports of kinetic studies deal with mechanisms of thermal oxidation of a variety of simple ketones monitored via gas evolution (CO, CO2, H2, etc.),176 alkaline oxidation of aldehydes with copper and silver tellurates,177 [Mlll(H2TcOf))2]5, and oxidation of acetals of simple aldehydes in aqueous acetic acid with (i) N-chlorobenzamide (H20C1+ is the oxidant inferred)178 and (ii) /V-chlorosaccharin.179... 

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