2- acetic acid formation from

Scheme 8.1 Acetic acid formation from CO, the role of CODH and tetrahydrofolate (THF).

Scheme 8. Acetic acid formation from methane. Methane (5 atm), VO(acac)2 (0.05 mmol), l<2S208 (5 mmol), TFA (20 mL), 80°C, 20 h.

In homogeneous system, Fukuoka et al.[64] found acetic acid formation from H2/CO2 and CHsI using bimetalhc catalysts system such as Ru3(CO)i2 + Co2(CO)8 and Ni(cod)2+Co2(CO)8 in DMF solvent at the condition of 4 Mpa, ISOT , H2/C02=l/1 and 24h. Acetic acid was produced with 50% selectivity and by product was mainly CO. Their proposed reaction mechanism was composed of CO2 insertion to Ru-CHs species, followed by hydrogenation of its intermediate to acetic acid by HCo(CO)4. ... 

There are two possible pathways to homologate methanol with carbon dioxide the CO2 insertion path and CO insertion path (Scheme 2). As for the former, Fukuoka et al. reported that the cobalt-ruthenium or nickel bimetallic complex catalyzed acetic acid formation from methyl iodide, carbon dioxide and hydrogen, in which carbon dioxide inserted into the carbon-metal bond to form acetate complex [7]. However, the contribution of this path is rather small because no acetic acid or its derivatives are detected in this reaction. Besides, the time course... 

Figure 3.3 View of the screw in the metering section of a 24 1 nonvented extruder. The hot melt flows around the downstream side of the mixing pins, where a sharp drop of pressure takes place. The area between the mixing pins and the flight is corroded as a result of steam explosion and acetic acid formation from hemicellulosics of the material.

The drawback of this reaction is that trifluoroacetic acid for the solvent and excess K2S2O8 for the oxidant are required. Although a bimetallic system based on Pd and Cu was initially used as the catalyst, it was determined that the reaction can proceed using only the copper catalyst. A radical mechanism is proposed. Vanadium complexes such as VO(acac)2 also effectively catalyze acetic acid formation from methane and CO (57). The yield reached 93% based on methane. 

These are initial rates of acetohydroxamic acid formation from acetic acid, catalyzed by nickel chloride. 

Infrared spectroscopy has also been employed to follow the formation of acetaldehyde and acetic acid on Pt during ethanol electro-oxidation. On the basal planes, acetaldehyde could be observed starting at about 0.4 V (vs. RHE), well before the onset of CO oxidation, while the onset of acetic acid formation closely follows CO2 formation [Chang et al., 1990 Xia et al., 1997]. This is readily explained by the fact that both CO oxidation and acetic acid formation require a common adsorbed co-reactant, OHads, whereas the formation of acetaldehyde from ethanol merely involves a relatively simple proton-electron transfer. 

Rowell etal. (1987b) produced PF-bonded flakeboard from acetylated southern pine (21.6 % WPG) or aspen (17.6 % WPG) flakes. This was not completely resistant to attack by termites Reticulitermes flavipes) in a 4-week test. It was thought that acetylation was less effective in preventing termite attack than other chemical modifications because cellulose decomposition in the intestines of termites leads to acetic acid formation in any case. 

Fig. 7. Enzyme-coupled assay in which the hydrolase-catalyzed reaction releases acetic acid. The latter is converted by acetyl-CoA synthetase (ACS) into acetyl-CoA in the presence of (ATP) and coenzyme A (CoA). Citrate synthase (CS) catalyzes the reaction between acetyl-CoA and oxaloacetate to give citrate. The oxaloacetate required for this reaction is formed from L-malate and NAD in the presence of L-malate dehydrogenase (l-MDH). Initial rates of acetic acid formation can thus be determined by the increase in adsorption at 340 nm due to the increase in NADH concentration. Use of optically pure (Ry- or (5)-acetates allows the determination of the apparent enantioselectivity i app i81)-...

It was found that a nickel-activated carbon catalyst was effective for vapor phase carbonylation of dimethyl ether and methyl acetate under pressurized conditions in the presence of an iodide promoter. Methyl acetate was formed from dimethyl ether with a yield of 34% and a selectivity of 80% at 250 C and 40 atm, while acetic anhydride was synthesized from methyl acetate with a yield of 12% and a selectivity of 64% at 250 C and 51 atm. In both reactions, high pressure and high CO partial pressure favored the formation of the desired product. In spite of the reaction occurring under water-free conditions, a fairly large amount of acetic acid was formed in the carbonylation of methyl acetate. The route of acetic acid formation is discussed. A molybdenum-activated carbon catalyst was found to catalyze the carbonylation of dimethyl ether and methyl acetate. 

Figure 7 shows the results of methyl acetate carbonylation in the presence of water. Methanol and dimethyl ether were formed up to 250 C suggesting that hydrolysis of methyl acetate proceeded. With increasing reaction temperature, the yield of acetic acid increased remarkably, while those of methanol and dimethyl ether decreased gradually. Figure 8 shows the effects of partial pressures of methyl iodide, CO, and methyl acetate in the presence of water. The rate of acetic acid formation was 1.0 and 2.7 order with respect to methyl iodide and CO, respectively. Thus, the formation of acetic acid from methyl acetate is highly dependent on the partial pressure of CO. This suggests that acetic acid is formed by hydrolysis of acetic anhydride (Equation 6) which is formed from methyl acetate and CO rather than by direct hydrolysis of methyl acetate. 

H, R = Me R = R = H, R = Me R> = R = Me, R = H R = OH, R = R = 9-Benzyloxymethylcarbazole and its 3-chloro, 3,6-dichlo-ro, and 3-nitro analogs gave comparable products (120) but only under acid catalysis. However, the use of acid with 9-hydroxymethylcarbazoles led to 3-substitution and the formation of 121 (R = H, Cl, and 9,9 -Dicarbazolylmethane is formed from 9-hydroxymethylcarbazole on treatment with acetic acid or from its acetate on reaction with carbazol-9-ylmagnesium iodide. ... 

The results of density functional theory (DFT) studies [90, 91] have suggested that the energy requirement via the C02 pathway is much less than that via the CO pathway, and thus the former is more thermodynamically favored. The methyl radical formation and dissociation of C02 are two rate-limiting steps for the synthesis of acetic acid directly from CH4 and C02. 

A new method for the synthesis of 1,4,5-oxadiazocines starting from /3-diketones with acidic a-hydrogens has been described (Scheme 28). The method involves formation of 2-hydroxyethylhydrazone 112 and sequential reaction with an aldehyde in the presence of acetic acid providing from moderate to good yields of 1,4,5-oxadiazocines 113 <2005TL8009>. 

Borisenko, K. B., Bock, C. W., and Hargittai, I., Geometrical consequences of intermolecular hydrogen bond formation in the formic acid and acetic acid dimers from ab initio MO calculations, J. Mol. Struct. (Theochem) 332, 161-169 (1995). 

Character of Center Nucleus.—As was stated in connection with anthracene itself we can not say positively as to the character of the center nucleus in either the hydrocarbon or the quinone. In anthracene the aliphatic character of this center nucleus is indicated by its formation from an ethane residue, by the tetra-brom ethane synthesis. This does not, however, preclude the possibility of its becoming a true benzene nucleus when condensed with two benzene rings, for benzene itself may be made from aliphatic hydrocarbons, from acetylene by polymerization (p. 478), and from hexane through hexa-methylene with the loss of hydrogen after the formation of the cyclo-paraffin (p. 469). Also naphthalene, in which there is no doubt of the benzene character of the two nuclei, may have one nucleus formed from an aliphatic chain as in the syntheses given (p. 767) from phenyl butylene bromide, from phenyl vinyl acetic acid and from tetra-carboxy ethane. In the same way the facts in regard to anthraquinone do not prove... 

In heterogeneous system, Hattori et al.[63] observed a direct formation of acetic acid from H2/CO2 over Ag-Rh(0.2-l)/SiO2 catalyst at the condition of 2 Mpa, 20013, GHSV=12000 and H2/C02=l/2. Carbon monoxide was a main product with 96% selectivity, however, acetic acid was produced with 2.4% selectivity. They speculated that direct insertion of CO2 to surface methyl species on Rh led acetate formation, followed by hydrogenation to acetic acid. Acetic acid formation was ascribed to a... 

Local effects are thought to be due to the formation of acetic acid resulting from hydrolysis of ethyl acetate. Central nervous system (CNS) depressive effects are thought to be due to a combination of absorbed ethyl acetate and formation of ethanol that results from hydrolysis. 

Cycloadditions. The scope of the Evans asymmetric aziridination is broadened by the ready availability of nitrene precursor 4-02NCjH S02N=IPh. The oxazolidinone-Af-acetic acid derived from (+)-cw-2-amino-l,2-diphenylethanol participates in p-lactam formation with imines. The predominant products (>99 1) have the (3/f,45)-configuration. The intramolecular [2+2]photocycloaddition involving a chiral allenylsilane moiety is an excellent method for accessing optically active methylenecyclobutane derivatives. ... 

A mechanism for the formation of 74 has been proposed [132] which has much in common with earlier ideas based on model studies by Eschenmoser and coworkers [119, 133, 134]. In addition, it is suggested that the dihydro form of 74 undergoes methylation at C-11, similar to that in Ps. denitrificans to yield 75. This could undergo a retro-aldol step to release acetaldehyde. Scheme 32. Indeed, when the 2-carbon fragment was immediately trapped, it was found to be acetaldehyde [135] the earlier isolation of acetic acid resulted from oxidation of acetaldehyde by long incubation with the mixture of enzymes. 

As it is seen from Scheme 3, central reaction of CA photolysis is photoreaction (3) of acetoxyalkyl radical Ri. presenting chain photoprocess of acetic acid formation. So, it is necessary to discuss the ideas on mechanism of acetic acid formation, being presented in literature. 

Photolysis of CDA runs with participation of two active centers acetylalkyl radicals R and polyene radicals P , which differ hard in reaction ability. Acetic acid is formed as a result of CDA photolysis, that is why protective action of the additive may be judged by the quantity of extracted acid. Kinetic curves of acetic acid formation at irradiation of stabilized CDA films by the light with wave length of 254 nm. In all cases dependence of the amount of formed acid on the time of irradiation is a strait line from the tangent of slope angle of which the rate of acetic acid formation has been calculated. As it is shown in Figure 4.1, HC - 2 has strong protective effect on the rate of CDA - films photodestruction. 

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