Ethanol, catalyzed oxidation

There are many ways to produce acetaldehyde. Historically, it was produced either hy the silver-catalyzed oxidation or hy the chromium activated copper-catalyzed dehydrogenation of ethanol. Currently, acetaldehyde is obtained from ethylene hy using a homogeneous catalyst (Wacker catalyst). The catalyst allows the reaction to occur at much lower temperatures (typically 130°) than those used for the oxidation or the dehydrogenation of ethanol (approximately 500°C for the oxidation and 250°C for the dehydrogenation). 

The above-described reverse reaction (viz. the Fe-catalyzed dehydrogenation of alcohols to ketones/aldehydes) has been reported by Williams in 2009 (Table 9) [58]. In this reaction, the bicyclic complex 16 shows a sluggish activity, whereas the dehydrogenation of l-(4-methoxyphenyl)ethanol catalyzed by the phenylated complex 17 affords the corresponding ketone in 79% yield when 1 equiv. (relative to 17) of D2O as an additive was used. For this oxidation reaction, l-(4-methoxyphenyl) ethanol is more suitable than 1-phenylethanol and the reaction rate and the yield of product are higher. 

Oxodedihydro Bisubstitution - Catalyzed Oxidation of Ethanol with HjOj to Acetic Acid... 

The catalyzed oxidation of ethanol to acetic acid is a well-studied reaction, carried out in continuous stirred tank reactors (CSTR) [51]. Hence it is a good test reaction for benchmarking micro reactor results. 

Organic synthesis 84 [OS 84] Catalyzed oxidations of ethanol with hydrc en peroxide to acetic acid... 

Many dehydrogenase enzymes catalyze oxidation/reduction reactions with the aid of nicotinamide cofactors. The electrochemical oxidation of nicotinamide adeniiw dinucleotide, NADH, has been studied in depthThe direct oxidation of NADH has been used to determine concentration of ethanol i s-isv, i62) lactate 157,160,162,163) pyTuvate 1 ), glucose-6-phosphate lactate dehydrogenase 159,161) alanine The direct oxidation often entails such complications as electrode surface pretreatment, interferences due to electrode operation at very positive potentials, and electrode fouling due to adsorption. Subsequent reaction of the NADH with peroxidase allows quantitation via the well established Clark electrode. 

Two possible interesting acetals are diethoxy ethane or butane. They can be synthesized by the catalyzed reaction of acetaldehyde (obtained by ethanol catalytic oxidation) with two molecules of ethanol, or by the catalyzed reaction of butanal (obtained by catalytic conversion of two molecules of acetaldehyde) with two molecules of ethanol. To achieve a one-pot synthesis, a key aspect for a possible commercial development, it is necessary to develop suitable multifunctional catalysts. Research on these aspects is in progress [63]. 

Poly(ethylene oxide) polymers and poly(ethylene oxide/propylene oxide) copolymers with iminodipropionitrile (139) or iminodiacetonitrile end groups were used as ligands in the palladium-catalyzed oxidation of higher olefins (1-octene to 1-hexadecene) at 50-70 °C with atmospheric air or 1-3 bar O2. In an ethanol/water mixture 88 % yield of 2-hexanone and 92 % yield of 2-hexadecanone was obtained in 4 and 2 h, respectively, with a... 

Similarly, catechin polymers formed upon horseradish peroxidase-catalyzed oxidation of catechin or polycondensation of catechin with aldehydes prove much more efficient than catechin (at identical monomer concentration) at inhibiting XO and superoxide formation. A more detailed investigation with the catechin-acetaldehyde polycondensate (which is expected to form in wine because of the microbial oxidation of ethanol to acetaldehyde) shows that inhibition is noncompetitive to xanthine and likely occurs via binding to the FAD or Fe/S redox centers involved in electron transfers from the reduced molybdenum center to dioxygen with simultaneous production of superoxide. 

Oxidation of ethanol. Although the major metabolic pathway for alcohols such as ethanol is oxidation catalyzed by alcohol dehydrogenase (see below), ethanol can also be metabolized by cytochrome P-450. The product, ethanal, is the same as produced by alcohol dehydrogenase. The isoform of cytochrome P-450 is CYP2E1. The mechanism may involve a hydroxylation to an unstable intermediate, which loses water to yield ethanal. Alternatively, a radical mechanism could be responsible. The importance of this route of metabolism for ethanol is that it is inducible (see chap. 5), assuming more importance after repeated exposure to ethanol such as in alcoholics and regular drinkers. 

T. Vuorinen, Alkali-catalyzed oxidation of glucose with sodium 2-anthraquinonesulfonate in ethanol-water solutions, Carbohydr. Res., 116 (1983) 61-69. 

Alcohol dehydrogenase catalyzes an oxidation the removal of two hydrogen atoms from the alcohol molecule. The oxidizing agent is nicotinamide adenine dinucleotide (NAD). NAD exists in two forms the oxidized form, called NAD+, and the reduced form, called NADH. The following equation shows that ethanol is oxidized to acetaldehyde, and NAD+ is reduced to NADH. 

The treatment for methanol or ethylene glycol poisoning is the same. The patient is given intravenous infusions of diluted ethanol. The ADH enzyme is swamped by all the ethanol, allowing time for the kidneys to excrete most of the methanol (or ethylene glycol) before it can be oxidized to formic acid (or oxalic acid). This is an example of competitive inhibition of an enzyme. The enzyme catalyzes oxidation of both ethanol and methanol, but a large quantity of ethanol ties up the enzyme, allowing time for excretion of most of the methanol before it is oxidized. 

A general method has been developed for utilization of cofactor-requiring enzymes in organic media [139]. ADH from horse liver as well as NADH were attached onto the surface of glass beads and afterwards suspended in a water-immiscible organic solvent containing the substrate. This method can be applied to other NAD+-dependent enzymes as well. Both NADH and NAD+ are efficiently regenerated with ADH-catalyzed oxidation of ethanol and reduction of isobutyr-aldehyde, respectively (Fig. 31). 

The cleavage of the intermediate allyl sulfenate can also be initiated under acidic conditions, e.g., by using catalytic amounts of 4-toluenesulfonic acid in ethanol or with thiophenol in dioxane5. By a combination of this method with the selenium dioxide catalyzed oxidation of allylic sulfides, a one-pot transformation of allylic sulfides to rearranged allylic alcohols was achieved. 

The MTT group has also been implicated in the intolerance to alcohol a.ssociatcd with certain injectable cephalosporins ccfamandole, cefotcian. ccfmetazolc, and cefoperazone. Thus, disulfiram-like reactions, attributed to the accumulation of acetaldehyde and resulting from the inhibition of aldehyde dehydrogenase-catalyzed oxidation of ethanol by M lT-contuining cephalo.sporins. " may occur in patients who have consumed alcohol before, during, or shortly after the course of therapy. 

Recently, Sen has reported two catalytic systems, one heterogeneous and the other homogeneous, which simultaneously activate dioxygen and alkane C-H bonds, resulting in direct oxidations of alkanes. In the first system, metallic palladium was found to catalyze the oxidation of methane and ethane by dioxygen in aqueous medium at 70-110 °C in the presence of carbon monoxide [40]. In aqueous medium, formic acid was the observed oxidation product from methane while acetic acid, together with some formic acid, was formed from ethane [40 a]. No alkane oxidation was observed in the absence of added carbon monoxide. The essential role of carbon monoxide in achieving difficult alkane oxidation was shown by a competition experiment between ethane and ethanol, both in the presence and absence of carbon monoxide. In the absence of added carbon monoxide, only ethanol was oxidized. When carbon monoxide was added, almost half of the products were derived from ethane. Thus, the more inert ethane was oxidized only in the presence of added carbon monoxide. 

Cuprous ammonium chloride. The combination of cuprous chloride and ammonium chloride in a slightly acidic aqueous solution catalyzes oxidative (air) coupling of terminal acetylenes to diacetyienes. - The groups NHa, OH, COjH, and COjR do not interfere, in the synthesis formulated, cross coupling was accomplished in a mixture of ethanol and 0.08 A hydrochloric acid containing the catalyst. 

In addition to enzymes, biological oxidations require substances known as coenzymes. Coenzymes are organic molecules that, in concert with an enzyme, act on a substrate to bring about chemical change. Most of the substances that we call vitamins are coenzymes. The coenzyme contains a functional group that is complementary to a functional group of the substrate the enzyme catalyzes the interaction of these mutually complementary functional groups. If ethanol is oxidized, some other substance must be reduced. This other substance is the oxidized form of the coenzyme nicotinamide adenine dinucleotide (NAD). Chemists and biochemists abbreviate the oxidized form of this... 

Industrial routes to acetic acid have included oxidation of ethanol derived from fermentation, hydrolysis of acetylene, and the oxidation of hydrocarbons such as butane or naphtha. In the late 1950s, the development of the Wacker process (a PdCl2/CuCT-catalyzed oxidation of ethylene) provided a route to acetaldehyde, which could be converted to acetic acid by subsequent oxidation. 

Most molecules of ethanol are detoxified in the liver by two reactions. In the first, ethanol is oxidized to form acetaldehyde. This reaction, catalyzed by alcohol dehydrogenase, produces large amounts of NADH ... 

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