Acetaldehyde ethanol oxidized

Currently, almost all acetic acid produced commercially comes from acetaldehyde oxidation, methanol or methyl acetate carbonylation, or light hydrocarbon Hquid-phase oxidation. Comparatively small amounts are generated by butane Hquid-phase oxidation, direct ethanol oxidation, and synthesis gas. Large amounts of acetic acid are recycled industrially in the production of cellulose acetate, poly(vinyl alcohol), and aspirin and in a broad array of other... 

There are two ways to produce acetaldehyde from ethanol oxidation and dehydrogenation. Oxidation of ethanol to acetaldehyde is carried out ia the vapor phase over a silver or copper catalyst (305). Conversion is slightly over 80% per pass at reaction temperatures of 450—500°C with air as an oxidant. Chloroplatinic acid selectively cataly2es the Uquid-phase oxidation of ethanol to acetaldehyde giving yields exceeding 95%. The reaction takes place ia the absence of free oxygen at 80°C and at atmospheric pressure (306). The kinetics of the vapor and Uquid-phase oxidation of ethanol have been described ia the Uterature (307,308). 

However, the reaction occurring in the acetaldehyde/ethanol half-cell is the oxidation of ethanol ... 

Ethanol is oxidized by alcohol dehydrogenase (in the presence of nicotinamide adenine dinucleotide [NAD]) or the microsomal ethanol oxidizing system (MEOS) (in the presence of reduced nicotinamide adenine dinucleotide phosphate [NADPH]). Acetaldehyde, the first product in ethanol oxidation, is metabolized to acetic acid by aldehyde dehydrogenase in the presence of NAD. Acetic acid is broken down through the citric acid cycle to carbon dioxide (CO2) and water (H2O). Impairment of the metabolism of acetaldehyde to acetic acid is the major mechanism of action of disulfiram for the treatment of alcoholism. 

Anton RF, Pettinati H, Zweben A, et al A multi-site dose ranging study of nalmefene in the treatment of alcohol dependence. J Clin Psychopharmacol 24 421 28, 2004 Aragon CM, Stotland LM, Amit Z Studies on ethanol-brain catalase interaction evidence for central ethanol oxidation. Alcohol Clin Exp Res 15 165-169, 1991 Arizzi MN, Correa M, Betz AJ, et al Behavioral effects of intraventricular injections of low doses of ethanol, acetaldehyde, and acetate in rats studies with low and high rate operant schedules. Behav Brain Res 147 203—210, 2003 Azrin NH, Sisson RW, Meyers R, et al Alcoholism treatment by disulfiram and community reinforcement therapy. J Behav Ther Exp Psychiatry 13 105—112, 1982 Babor TF, Kranzler HR, Lauerman RL Social drinking as a health and psychosocial risk factor Anstie s limit revisited, in Recent Developments in Alcoholism, Vol 5. Edited by Galanter M. New York, Plenum, 1987, pp 373 02... 

Another metal that has attracted interest for use as electrode material is rhodium, inspired by its high activity in the catalytic oxidation of CO in automotive catalysis. It is found that Rh is a far less active catalyst for the ethanol electro-oxidation reaction than Pt [de Souza et al., 2002 Leung et al., 1989]. Similar to ethanol oxidation on Pt, the main reactions products were CO2, acetaldehyde, and acetic acid. Rh, however, presents a significant better CO2 yield relative to the C2 compounds than Pt, indicating a... 

The mechanism of ethanol oxidation is less well established, but it apparently involves two mechanistic pathways of approximately equal importance that lead to acetaldehyde and ethene as major intermediate species. Although in flow-reactor studies [45] acetaldehyde appears earlier in the reaction than does ethene, both species are assumed to form directly from ethanol. Studies of acetaldehyde oxidation [52] do not indicate any direct mechanism for the formation of ethene from acetaldehyde. 

Because the initial oxygen concentration determines the relative abundance of specific abstracting radicals, ethanol oxidation, like methanol oxidation, shows a variation in the relative concentration of intermediate species according to the overall stoichiometry. The ratio of acetaldehyde to ethene increases for lean mixtures. 

In addition to alcohol dehydrogenase, ethanol can be oxidized to acetaldehyde by the microsomal mixed-function oxidase system (cytochrome P450 2 El), as illustrated in Figure 35.1. Although this microsomal ethanol-oxidizing system probably has minor impor-... 

Reactions of anthocyanins and flavanols take place much faster in the presence of acetaldehyde that is present in wine as a result of yeast metabolism and can also be produced through ethanol oxidation, especially in the presence of phenolic compounds, or introduced by addition of spirit in Port wine technology. The third mechanism proposed involves nucleophilic addition of the flavanol onto protonated acetaldehyde, followed by protonation and dehydration of the resulting adduct and nucleophilic addition of a second flavonoid onto the carbocation thus formed. The resulting products are anthocyanin flavanol adducts in which the flavonoid units are linked in C6 or C8 position through a methyl-methine bond, often incorrectly called ethyl-link in the literature. 

Propanol oxidation under mild conditions takes place with high selectivity. No products other than acetone were observed in the ATR spectra recorded in situ. The situation is more complex for the oxidation of primary alcohols such as ethanol. The first oxidation step produces acetaldehyde, which is prone to further reactions, as is apparent in the ATR spectra. Figure 20, left, shows ATR spectra recorded in situ during ethanol oxidation. Figure 20, right, shows some signals as a function of time. The experiment was performed in a manner similar to that of the one... 

Acetaldehyde is oxidized to acetic acid by NAD+-dependent aldehyde dehydrogenases (ALDH) in liver and nasal mucosal preparations. Its administration to rats causes an increase in urinary excretion of sulfur metabolites and it is known to react with cysteine to produce a thiazolidine 4-carboxylic acid derivative that can be A -nitro-sated in vivo upon co-administration of nitrite (lARC, 1985). Many studies have been published subsequently, but these have been mainly in the context of ethanol metabolism. 

This is the free-eneigy change for the oxidation-reduction reaction at pH 7, when acetaldehyde, ethanol, NAD+, and NADH are all present at 1.00 m concentrations. If, instead, acetaldehyde and NADH were present at 1.00 Mbut ethanol and NAD+ were present at 0.100 m, the value for AG would be calculated as follows. First,... 

Acetaldehyde. The industrial production of acetaldehyde by the hydration of acetylene has lost its importance with the introduction of more economical petrochemical processes (dehydrogenation of ethanol, oxidation of ethylene see Section 9.5.2). At present it is practiced only in a few European countries where relatively cheap acetylene is still available.86-88... 

TPPS)Fe-O-Fe(TPPS)]8" 2 [Fe"(TPPS)]4" Solvent water + ethanol Xilr = unspecified ethanol oxidized to acetaldehyde [255]... 

Oxidation of compounds of the types thus far discussed proceeds readily at room temperature. Certain compounds which show no substantial reaction with periodic acid at room temperature can be oxidized at elevated temperature.22- 23 26 Thus, at 100° in aqueous solution the acetone mole exile is split to produce acetic acid and formaldehyde diethyl ketone yields propionic acid and probably ethanol lactic acid gives acetaldehyde and carbon dioxide acetaldehyde is oxidized to formic acid and methanol, which is converted into formaldehyde and pyruvic acid yields acetic acid and carbon dioxide. 

Oyama and Somorjai have studied the oxidation of ethanol and ethane over vanadia supported on silica.33 Ethane oxidation yielded ethylene and acetylene with considerable CO2 for highly dispersed catalysts. Ethanol oxidation to acetaldehyde, on the other hand was shown to be structure insensitive. Conversions and selectivities for reaction of ethanol are shown in Table III.33... 

Acetic Acid. Acetic acid is the most important carboxylic acid produced industrially. The annual production in the United States in 1999 was almost 15.7 billion lb. As with many compounds produced on a large scale, acetic acid has several different commercial processes. The carbonylation of methanol is now the dominant route. (This process was described earlier in this chapter in the section Methanol .) The oxidation of acetaldehyde, ethanol, and butane are also important. The percent world capacity for virgin acetic acid... 

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