Ketones oxidant

Ketones oxidize about as readily as the parent hydrocarbons or even a bit faster (32). Although the reactivities of hydrogens on carbons adjacent to carbonyl groups are perhaps doubled, the effect is small because one methylene group is missing in comparison to the parent hydrocarbon. Ketones oxidize less readily than similar primary or secondary alcohols (35). 

Acids are usually the end products of ketone oxidations (41,42,44) but vicinal diketones and hydroperoxyketones are apparent intermediates (45). Acids are readily produced from vicinal diketones, perhaps through anhydrides (via, eg, a Bayer-ViUiger reaction) (46,47). The hydroperoxyketones reportedly decompose to diketones as well as to aldehydes and acids (45). Similar products are expected from radical— radical reactions of the corresponding peroxy radical precursors. 

Oxidation. Ketones are oxidized with powerful oxidizing agents such as chromic or nitric acid. During oxidation, carbon—carbon bond cleavage occurs to produce carboxyHc acids. Ketone oxidation with hydrogen peroxide, or prolonged exposure to air and heat, can produce peroxides. Concentrated solutions of ketone peroxides (>30%) may explode, but dilute solutions are useful in curing unsaturated polyester resin mixtures (see... 

BAEYER VILLIQER Ketone Oxidation Synthesis of esters or lactones trom ketones with retention of configuration... 

The choice of which reactions to include is not an easy one. First there are the well known "Name Reactions", that have appeared in various monographs or in the old Merck index. Some of these are so obvious mechanistically to the modern organic chemistry practitioner that we have in fact omitted them for instance esterification of alcohols with acid chlorides - the Schotten-Baumann procedure. Others are so important and so well entrenched by name, like the Baeyer-Villiger ketone oxidation, that it is impossible to ignore them. In general we have kept older name reactions that are not obvious at first glance. 

Condensation between carboxylic esters and aldehydes or ketones Addition of a-metalated esters to ketones Oxidation of methylene to OH, O2CR, or OR... 

Intramolecular Friedel-Crafts acylation of diaryl ketones Oxidation of phenols or aromatic amines Oxidation of aromatic hydrocarbons... 

Discussion of ketone oxidation has centred around the identity of the molecule undergoing oxidation. This has been clearly resolved in some, but not all, cases, the evidence resting on (i), the relative rates of enolisation and oxidation, (ii) kinetic orders and (ih) isotope effects. A general feature of the oxidations of ketones by one-equivalent reagents is that the rate for a given oxidant exceeds that for oxidation of a secondary alcohol by the same oxidant. The most attractive explanation is that the radical formed from a ketone is stabilised by delocalisation, viz. 

Selenium dioxide can be used to oxidize ketones and aldehydes to a-dicarbonyl compounds. The reaction often gives high yields of products when there is a single type of CH2 group adjacent to the carbonyl group. In unsymmetrical ketones, oxidation usually occurs at the CH2 that is most readily enolized.255... 

Kinetic analysis of the results of ketone oxidation in the presence of amine II reveals that the velocity constant of the oxidation of amines by acyl per-oxy radicals must be greater (by a factor of 2 - 3) than that of the interaction of these radicals with the nitroxide-i. In this reaction, acyl peroxy radicals are captured and destroyed by amines. 

Other mechanisms of ketone oxidation are also known and will be discussed in Chapter 8. Peracid, which is formed from aldehyde, oxidizes ketones with lactone formation (Bayer-Villiger reaction). 

Ketones, like hydrocarbons and other organic compounds, are oxidized by dioxygen via the chain mechanism [4,62]. The carbonyl group weakens the adjacent C—H bond. Therefore, a peroxyl radical attacks the a-C—H bond as this bond is the most reactive in a ketone. The pecularities of ketone oxidation are the same as aldehyde oxidation. 

The first intermediate product of ketone oxidation is a-ketohydroperoxide. All other molecular products are formed by decay and reactions of this hydroperoxide and its adduct with ketone. Among these products, aldehydes, diketones, a-hydroxyketones, acids, esters, and C02 were observed. The information about the products of the oxidation of ketones by dioxygen are available in monographs [4,7],... 

Two carboxylic acids are the final products of this ketone oxidation. As a result, the content of ketones in the system decreases, and the yield of aliphatic acids increases. 

Aryl and alkyl hydroxylations, epoxide formation, oxidative dealkylation of heteroatoms, reduction, dehalogenation, desulfuration, deamination, aryl N-oxygenation, oxidation of sulfur Oxidation of nucleophilic nitrogen and sulfur, oxidative desulfurization Oxidation of aromatic hydrocarbons, phenols, amines, and sulfides oxidative dealkylation, reduction of N-oxides Alcohol oxidation reduction of ketones Oxidative deamination... 

Carlsson and Wiles have in an early work (14) discussed the ketonic oxidation products of PP films. The volatile products were analysed in GC with a flame ionization detector (FID) and a thermal conductivity detector (TCD) giving the major oxidation products carbon monoxide and acetone. Other products detected were water, formaldehyde, formic acid, propane, acetic acid and iso-propylalcohol. 

Aldehydes easily oxidize to carboxylic acids or to carboxylates. In fact, preventing the oxidation of an aldehyde is difficult. Ketones oxidize with difficulty, since a change in the backbone must first take place. 

Por other examples of secondary alcohol to ketone oxidations in Chapter 1 cf. 2.3.6. 

Bis(trifluoromethyl) peroxycarbonate, 705 Bis(trifluoromethyl) peroxydicarbonate, 705 Bis(trifluoromethyl) trioxide IR spectrum, 740 O NMR spectroscopy, 182 Bis(trifluoromethyl) tiioxydicarbonate, 740 Bis(trimethylsilyl) monoperoxysulfate Baeyer-Vilhger oxidation, 785 catalytic epoxidation, 791-2 Bis(trimethylsilyl) peroxide (BTSP) alcohol oxidation, 787-90 alkyne reactions, 800 aromatic compounds, 794-5 Baeyer-Vilhger ketone oxidation, 784-7 demethylation, 798... 

Baeyer-ViUiger ketone oxidation, 785 C-H hond oxygen insertion, 1138-9, 1158-63... 

Figure 1. Chemiluminescence exhibited by methyl ethyl ketone oxidation in benzene solution at 60°C. Arrow shows time of adding initiator Y...

The effect of solvents on the rate constants for chain propagation and termination was investigated for methyl ethyl ketone oxidation. The rate of the latter at temperatures of 35° to 75°C. was determined from that of oxygen consumption (11). Azoisobutyronitrile was used as initiator. The rates of chain initiation, wh for various solvents were measured using the inhibitor technique (I). Knowing W, the methyl ethyl ketone concentration, and wiy it was possible to calculate the k2/ y/ k ratio. 

The close values of /x2 and /x6 obtained for various solvents provide additional evidence that variations in the k2 and k values are related solely to the dielectric constant of the medium, while specific solvation— e.g., the formation of 7r-complexes of R02 radicals and aromatics in the course of methyl ethyl ketone oxidation—has no essential importance. 

Table V. Rate Constants (60°) for Chain Propagation and Termination and Pre-exponential Factors and Activation Energies for Methyl Ethyl Ketone Oxidation in Aqueous Solutions...

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