Oxidation of Mono-Alcohols

In the oxidation of mono-alcohols, in particular aliphatic and aromatic alcohols, Au/ metal oxides have attracted more attention than Au NPs supported on activated carbon (AC) owing to the relatively higher catalytic activity and because of the 

The aerobic oxidation of alcohol under neutral or acidic conditions to produce the corresponding adds, which can avoid the neutralization of the carboxylate salts, is also an important R D issue. In Au-catalyzed alcohol oxidation in methanol, the corresponding methyl esters are obtained with high seledivity instead of carboxylic acids by using metal oxide supported Au NPs [157, 160], In this case, base is not necessary, or only a catalytic amount of base is required to promote the readion. However, in water, it was demonstrated that alcohols were not oxidized under acidic conditions [161] and only aldehydes were oxidized to carboxylic adds [162]. Even under solvent-free conditions or in organic solvents, alcohols were converted into aldehydes without base however, the alcohols were not fully oxidized to carboxylic acid under acidic conditions [163-166]. 

Bioethanol can be regarded as a potential renewable feedstock and is produced as 3-15 vol.% aqueous solution by fermentation. Therefore, the dired transformation of dilute bioethanol to valuable compounds with air can be an environmentally friendly process. Gold catalysts appear to be advantageous in this process over Pd and Pt catalysts. The latter showed inferior seledivity to acetic acid of 60% and 16% for Pd and Pt, respedively, under the same conditions [167]. Furthermore, C02, which can be easily removed from the produd solution, was formed as the major by-produd over Au catalysts, whereas acetaldehyde was also co-produced over Pd and Pt catalysts. 

Another growing research interest is the scope of support materials for Au NPs, since catalytic performance markedly depends on the size of Au particles and the interaction between Au and the supports. In particular, organic polymers have received attention as a new kind of support for Au NPs, because polymers are expected to not only act as a support to stabilize small Au N Ps and clusters but also to provide a suitable reaction environment through the design of polymer structures and surface modifications [11]. 

Miyamura et al. [170] and Kanaoka et al. [171] have succeeded in stabilizing Au clusters on polymer supports for aerobic oxidation at room temperature in the mixed solvent of water-benzotrifluoride and in water, respectively. Polymer supports could also offer new functions, such as a recycling system by using a thermoresponsive polymer-supported Au catalyst [171]. 

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Gold NPs deposited on carbons are active and selective for mild oxidations in liquid phase although they exhibit almost no catalytic activity in the gas phase. Examples are aerobic oxidation of mono-alcohols, diols, glycerol, glucose, alkenes and alkanes. 

Oxidation of isopropyl alcohol by chromic acid in concentrated acetic acid solution has recently been studied by Wiberg and Schafer S spectrophotometri-cally. At 385 nm a rapid increase in absorbance (with a half life of about 6 sec) due to mono- and diester formation was noted. When the reaction was examined at 510 nm, first a rapid increase, then a decrease of the absorbance was found. Since at this wavelength only chromium species can absorb, the intermediate could be chromium(V) or (IV). The esr spectra of reaction mixtures showed a relatively sharp signal with a. g = 1.9805 value corresponding to chromium(V). The fact that the relative concentrations of the intermediate determined from the spectral data agree well with the intensity of esr signals, indicates that the same species is responsible for the both phenomena. It is then clear that the oxidation of isopropyl alcohol proceeds via chromium(V). 

Oxidation of unsaturated oleochemicals can proceed in different ways, and yields numerous products. Typical oxidations of fatty acids are, for instance, ketoniza-tions yielding keto acids [72, 73], hydroxylations to bishydroxy acids [74], epoxida-tions to epoxy acids [75-78] and oxidative splitting reactions [72, 74] yielding mixtures of mono- and dicarboxylic acids. However, not only the double bond but also the functional group of the fatty compound, can be oxidized. One example is the ruthenium-catalyzed oxidation of fatty alcohols to fatty aldehydes or fatty acids... 

For the synthesis of peraksine (223), the aldehyde functionality of 228 was converted into a dimethyl acetal in 93% yield, and this was followed by hydroboration/oxidation to mono-alcohol 233 (Scheme 14). Upon heating the mono-alcohol 233 under acidic conditions the hemiacetal ring was formed intramolecularly to obtain peraksine (223) as an epimeric mixture at C-17 in 52% yield. 

A synthesis of the related sesquiterpenoid pentalene, 26, also began with the Weiss-Cook reaction product 12 (R = R" = H). Wittig olefination was carried out on the mono-ketal of 12 followed by hydrolysis of the ketal. The resultant ketone was reduced to the corresponding alcohol and the exocyclic alkene underwent cyclopropanation to produce 23. Oxidation of the alcohol generated a ketone that could be converted to the enone using the... 

On the basis of the obtained results it is possible to make the following conclusion. The kinetics of ozone consumption in the reaction with the PVA described by the second order reaction law (the first - on ozone and the first - on substrate). Similar pattern, as noted above, is typical for ozone oxidation of mono- and diatomic alcohols in the field of small concentrations of the substrate and it is not typical for the oxidation of alcohols with higher atomicity (with the number of OH-groups n > 3) - glycerine, ethriole, pentaerythritol and mannitol. Obviously, here is implemented the following ratio k + k3[S] K (see the scheme at the beginning of the article). Thus, all the obtained complexes S—O3 ([S—O3] [O3]) are transformed into products and, consequently, the rate of ozone consumption is determined by the rate of the reaction (1) ... 

This activity refers to the oxidation of primary alcohols to aldehydes and of secondary alcohols to ketones, as well as to the corresponding reverse reductions. Besides simple aliphatic mono and polyalcohols, such as ethanol and ethylene glycol, some steroids, such as 3-keto and 3-beta-hydroxysteroids have also been found to... 

The specificity of animal diamine oxidase has been reinvestigated by Fonts et al. (119). Hog kidney cortex served as the source of partially purified diamine oxidase. According to these workers monoamine oxidase is easily separated from diamine oxidase since monoamine oxidase is exclusively present in particulate matter (however, see I40). Twenty-six monoamines (aliphatic monoamines, amino alcohols, phenylalkylmonoamines) were tested and thirteen were shown to be attacked by diamine oxidase, although much less readily than the diamines. Semicarbazide (111, 187) and aminoguanidine (188), which do not effect monoamine oxidase, blocked the oxidation and deamination of the monoamines. In contrast, the oxidation was not affected by iproniazid, a powerful inhibitor of monoamine oxidase but not of diamine oxidase (169-161). Simultaneous oxidation of mono-and diamines did not lead to additive oxidation rates. In view of these results it was concluded that mammalian diamine oxidase does attack monoamines at a reduced rate. Apparently the second basic group of the diamines is not required for the formation of the enzyme substrate complex... 

Yamada and coworkers (Yamada et al., 1993) reported on the cyclization reaction of mono-substituted alkenes with )6-ketoesters, in presence of molecular oxygen and catalytic amounts of CAN. The reaction yielded substituted l,2-dioxan-3-ols. CAN supported on charcoal (CAN-charcoal) is a catalyst for the air oxidation of benzyl alcohols to benzaldehydes and a-hydroxyketones (acyloins) into cy-diketones (Hatanaka et al., 1983) (scheme 63). 

Prepared by epoxidation of styrene with per-oxyelhanoic acid. Reactions are similar to those of aliphatic epoxides (s e, e.g. ethylene oxide). Reacts with alcohols to give mono-ethers, e g. PhCH(0Me)CH20H. Phenols give resins. 

Mixed mono- and dialkyl are used as catalysts for resin curing and as intermediates for fire retardants, oil additives, antistatic agents (qv), and extraction solvents. An equimolar mixture of mono- and dialkyl acid phosphates are formed at a 1 6 mole ratio of oxide to alcohol. 

Glycol Ethers. Glycol ethers are produced by reaction of propylene oxide with various alcohols such as methanol, ethanol, butanol, and phenol. The products are the mono-, di-, and tripropylene glycol ethers. These products are used in protective coatings, inks, textile dyeing, cleaners, antiicing additives for jet fuel, and as chemical intermediates (276). 

Sulfation andSulfamation. Sulfamic acid can be regarded as an ammonia—SO. complex and has been used thus commercially, always in anhydrous systems. Sulfation of mono-, ie, primary and secondary, alcohols polyhydric alcohols unsaturated alcohols phenols and phenolethylene oxide condensation products has been performed with sulfamic acid (see Sulfonation and sulfation). The best-known appHcation of sulfamic acid for sulfamation is the preparation of sodium cyclohexylsulfamate [139-05-9] which is a synthetic sweetener (see Sweeteners). 

The isotopic purity of the product is usually about 48-62%, the rest of the material being mainly undeuterated. (An alternate preparation of a-mono-deuterio ketones of high configurational and isotopic purity is the mild oxidation of cis- or tra 5-deuterated alcohols under Jones conditions, see sections V-D and VII-A.) Treatment with zinc in acetic acid-OD has also been applied to the deiodination of 2a-iodoandrost-4-ene-3,17-dione. In a slightly modified version the iodine in 19-iodocholesterol acetate has been replaced with tritium by using tritium oxide as the isotope source/... 

Clear, surface-active phosphate ester compositions were prepared by heating 1 mol P4O,0 with 2-4.5 mol of a linear or branched chain C6, 8 saturated alcohol, a C4 20 mono- or dialkylphenol, or a 2- to 14-mol ethylene oxide adduct of one of these alcohols or alkylphenols at 25-110°C, and hydrolyzing the reaction product at 60-110°C with 0.5-3.0% H20. The hydrolyzed mixture had a lower Klett color value than the phosphorylation reaction mixture [21]. 

Hydroxycarbonylation and alkoxycarbonylation of alkenes catalyzed by metal catalyst have been studied for the synthesis of acids, esters, and related derivatives. Palladium systems in particular have been popular and their use in hydroxycarbonylation and alkoxycarbonylation reactions has been reviewed.625,626 The catalysts were mainly designed for the carbonylation of alkenes in the presence of alcohols in order to prepare carboxylic esters, but they also work well for synthesizing carboxylic acids or anhydrides.137 627 They have also been used as catalysts in many other carbonyl-based processes that are of interest to industry. The hydroxycarbonylation of butadiene, the dicarboxylation of alkenes, the carbonylation of alkenes, the carbonylation of benzyl- and aryl-halide compounds, and oxidative carbonylations have been reviewed.6 8 The Pd-catalyzed hydroxycarbonylation of alkenes has attracted considerable interest in recent years as a way of obtaining carboxylic acids. In general, in acidic media, palladium salts in the presence of mono- or bidentate phosphines afford a mixture of linear and branched acids (see Scheme 9). 

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