Oxidative acetate

Other reagents which oxidize acetals such as ozone and TV -bromosuccinimide show similar reactivitjrtrepds. ... 

The cycle shown in Figure 20.4 at first appears to be a complicated way to oxidize acetate units to COg, but there is a chemical basis for the apparent complexity. Oxidation of an acetyl group to a pair of COg molecules requires C—C cleavage ... 

Until now we have viewed the TCA cycle as a catabolic process because it oxidizes acetate units to COg and converts the liberated energy to ATP and reduced coenzymes. The TCA cycle is, after all, the end point for breakdown of food materials, at least in terms of carbon turnover. However, as shown in Figure 20.22, four-, five-, and six-carbon species produced in the TCA cycle also fuel avariety of biosynthetic processes. a-Ketoglutarate, succinyl-CoA, fumarate, and oxaloacetate are all precursors of important cellular species. (In order to par-... 

A solution of 10 g (0.023 mole) of cholesteryl acetate (mp 112-114°) in ether (50 ml) is mixed with a solution containing 8.4 g (0.046 mole) of monoperphthalic acid (Chapter 17, Section II) in 250 ml of ether. The solution is maintained at reflux for 6 hours, following which the solvent is removed by distillation (steam bath). The residue is dried under vacuum and digested with 250 ml of dry chloroform. Filtration of the mixture gives 6.7 g of phthalic acid (87% recovery). The solvent is evaporated from the filtrate under reduced pressure and the residue is crystallized from 30 ml of methanol, giving 6.0 g (58% yield) of -cholesteryl oxide acetate. Recrystallization affords the pure product, mp 111-112°. Concentration of the filtrate yields 1.55 g (15% yield) of a-cholesteryl oxide acetate which has a mp of 101-103° after crystallization from ethanol. 

Chloro-1 -dihvdro-5-phenvl-2H-1,4-benzodiazepin-2-one-4-oxide Acetic anhydride Sodium hydroxide... 

This organism is able to oxidize acetate to CO2 under anaerobic conditions in the presence of Fe(III). A study of the intermediate role of humic and fulvic acids used ESR to detect and quantify free radicals produced from oxidized humic acids by cells of G. metallireducens in the presence of acetate. There was a substantial increase in the radical concentration after incubation with the cells, and it was plausibly suggested that these were semiquinones produced from quinone entities in the humic and fulvic structures (Scott et al. 1998). 

It is well established that the main products of ethanol electro-oxidation on Pt in acidic media are acetaldehyde and acetic acid, partial oxidation products that do not require C—C bond breaking, with their relative yields depending on the experimental conditions [Iwasita and Pastor, 1994]. Apart from the loss of efficiency associated with the partial oxidation, acetic acid is also unwanted, as it constitutes a catalyst poison. 

B. Pyridine-N-oxide. The acetic acid solution is evaporated on the steam bath under the pressure of a water aspirator, and the residue (180-190 g.) is distilled at a pressure of 1 mm. or less in an apparatus suitable for collecting a solid distillate (Note 5). The vacuum pump must be protected with a Dry Ice trap capable of holding about 60 ml. of acetic acid, which distils as the pyridine-N-oxide acetate dissociates at low pressure. Heat is provided by an oil bath, the temperature of which is not allowed to rise above 130° (Note 6). The product is collected at 100-105°/1 mm. (95-98°/0.5 mm.). The yield is 103-110 g. (78-83%) of colorless solid, m.p. 65-66° (sealed capillary). The base is deliquescent and must be stoppered immediately. 

See 3-Methyl-4-nitropyridine /V-oxide Acetic acid, Jute... 

The chemical composition of B. papyrifera olibanum is markedly different from that of other Boswellia, with small amounts of monoterpenes and sesquiterpenes, large amounts of w-octanol (18) and -octy I acetate (40), with the latter being the major compound, and the presence of particular diterpenes [incensole (127), incen-sole acetate (129), incensole oxide (130) and incensole oxide acetate (131)] and the absence of both isoincensole and isoincensole acetate (128). Linear carboxylic acids from hexanoic acid (10) to lauric acid (93) were also identified in B. papyrifera olibanum exclusively. 

Figure 10.7 Total ion current chromatograms obtained after headspace SPME for (a) incense from Mount Athos and (b) B. papyrifera olibanum. Peak labels correspond to compound identification given in Table 10.3. The occurrence of the following biomarkers of B. papyrifera olibanum in the incense from Mount Athos are a clear indication of its botanical origin n octanol (18), n octylacetate (40), incensole (127), incensole acetate (129), incensole oxide (130) and incensole oxide acetate (131). Artefacts. Reproduced from S. Hamm, J. Bleton,). Connan, A. Tchapla, Phytochemistry, 66, 1499 1514. Copyright 2005 Elsevier Limited...

Another elegant use of nonadienoate is the synthesis of a pheromone called brevicomin (148) (132). The ester was converted to 1,6-nonadiene (149). The terminal double bond was selectively converted to glycol via epoxide. The oxidation with PdCI2 produced brevicomin directly by intramolecular oxidative acetal formation. 

Carboxylic acids are thermally stable. Decarboxylation of carboxylic acids is observed at 600 K and higher in the absence of dioxygen [4], At the same time, the decarboxylation of fatty acids in oxidized cumene was observed at 350 K [71]. The study of C02 production from oxidized acetic, butanoic, isobutanoic, pentanoic, and stearic acids labeled with 14C in the... 

Respiration, as we have described, drives two half-reactions, one to donate electrons and one to accept them. Iron-reducing bacteria, for example, can live on acetate, which is produced during the breakdown of organic matter. Oxidizing acetate provides electrons,... 

By the late 1930s it was widely accepted that active acetate arose from pyruvate decarboxylation and fatty acid oxidation. Acetate itself... 

Although potassium permanganate does not oxidize acetals in aqueous media, with a phase-transfer catalyst under non-aqueous conditions, cyclic acetals are converted into hydroxyalkyl carboxylates [36]. 

These short-chain fatty acids are acetic, butyric, lactic and propionic acids, also known as volatile fatty acids, VFA. They are produced from fermentation of carbohydrate by microorganisms in the colon and oxidised by colonocytes or hepatocytes (see above and Chapter 4). Butyric acid is activated to produce butyryl-CoA, which is then degraded to acetyl-CoA by P-oxidation acetic acid is converted to acetyl-CoA for complete oxidation. Propionic acid is activated to form propionyl-CoA, which is then converted to succinate (Chapter 8). The fate of the latter is either oxidation or, conversion to glucose, via glu-coneogenesis in the liver. 

Protection of an alcohol function by esterification sometimes offers advantages over use of acetal or ether groups. Generally, ester groups are stable under acidic conditions. Esters are especially useful in protection during oxidations. Acetates and benzoates are the most commonly used ester derivatives. They can be conveniently prepared by reaction of unhindered alcohols with acetic anhydride or benzoyl chloride, respectively, in the presence of pyridine or other tertiary amines. 4-Dimethylaminopyridine (DMAP) is often used as a catalyst. The use of A-acylimidazolides (see Section 3.4.1) allows the... 

Triflouroacetic anhydride was used before oxalyl chloride and is also known as the Swern Oxidation. Acetic anhydride can also be used. (Albright-Goldman Oxidation)... 

It has been used as a solvent and as an intermediate in the manuf of chemicals used in the expl industry and of synthetic rubber (Ref 4). During WWII, acetal(as well as acetaldehyde) was used in Germany as hyper-gollic fuel in liquid rocket propellants in conjunction with red or white fuming nitric acid which served as an oxidizer. Acetal was later replaced by ca te ch o 1( Bren zc ate chin or Brenzol in Ger)(Ref 10)... 

Zinc amalgam, or electrochemical reduction of porphyrinatoniobium(V) oxide acetates led to [NbIVOL] (L = OEP, TPP, TPTP).566 The [NbOLF]- anions have been obtained by controlled potential electrolysis of (i) the corresponding Nbv oxo acetate in the presence of PFg and (ii) the appropriate Mr oxo fluoride. Reduction by zinc amalgam of [M)LX3] (X = Q, Br) gave [NbtvLX2] 327 the ESR spectra of the six-coordinate complexes in frozen THF solution are consistent with trans coordination. 

Epoxide formation is nearly suppressed when massively subeti-tuted olefine, such as 2,2,4-trimethyl-3-hexene among others, ate subjected to the chromic oxide-acetic anhydride reagent,42 Cyclo-hexene yields primarily 2-cyclohexenone and cyclohexane- 1,2-dione777 although some cyclohexane oxide appears to bo formed also (Eq, 111). 

Acetic acid,127 pyridinium trifluoroacetate (PTFA)121 or pyridinium tosylate (PPTS)128 are often added in order to speed up PDC oxidations. Acetic acid, which is described as superior127a and very easy to remove, is used most often. Although this precludes the advantages of using an almost neutral PDC medium, it provides a very useful substantial acceleration of the oxidations. The combined employment of molecular sieves and an acid can provide a synergistic accelerating effect.127a... 

Albright-Goldman Oxidation (Acetic Anhydride-Mediated Moffatt Oxidation)... 

Ohsaka and co-workers658 have reported a new method to prepare peroxyacetic acid by oxidizing acetic acid with H202 in the presence of Nafion catalysts. Nafion-H proved to be superior to Nafion SAC-13 to give a conversion of 16% (5% of catalyst, initial reactant concentrations [CH3COOH] = 1.65 M, [H202] = 2.85 M, 17 h). 

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