Acetate radical, decomposition

It is possible that some acetate radicals are formed by the direct discharge of the ions as, it will be seen shortly, is the case in non-aqueous solutions but an additional mechanism must be introduced, such as the one proposed above, to account for the influence of electrode material, catalysts for hydrogen peroxide decomposition, etc. It is significant that the anodes at which there is no Kolbe reaction consist of substances that are either themselves catalysts, or which become oxidized to compounds that are catalysts, for hydrogen peroxide decomposition. By diverting the hydroxyl radicals or the peroxide into an alternative path, viz., oxygen evolution, the efficiency of ethane formation is diminished. Under these conditions, as well as when access of acetate ions to the anode is prevented by the presence of foreign anions, the reactions mentioned above presumably do not occur, but instead peracetic acid is probably formed, thus,... 

The most common polymer of a vinyl ester is poly(vinyl acetate), CAS 9003-20-7, with the formula [-CH2CH(OC(0)CH3)-]n. Other vinyl esters also are known, such as poly(vinyl butyrate), poly(vinyl benzoate) CAS 24991-32-0, and poly(vinyltrifluoroacetate), CAS 25748-85-0. Poly(vinyl acetate) is typically obtained from the monomer with radical initiators, either by emulsion or suspension polymerization. The polymer Is used in water-based emulsion paints, adhesives [22], gum base for chewing gum, etc. Also, poly(vinyl acetate) is used as a precursor for the preparation of other polymers such as poly(vinyl alcohol) or poly(vinyl acetals). Thermal decomposition of poly(vinyl acetate) starts at a relatively low temperature, around 200° C, some of the reports regarding its thermal decomposition being given in Table 6.5.8 [13]. The same table includes references for poly(vinyl butyrate) and poly(vinyl cinnamate), CAS 9050-06-0. 

The rate constant of the reaction of cobalt(III) acetate with benzaldehyde in the absence of dioxygen was determined in independent experiments. It turned out to be virtually the same as the rate constant of the chain initiation in the oxidation reaction in the presence of O2- However, the contribution of chain initiation to the radical formation is insignificant in the developed oxidation process. The radicals are mainly formed in the reactions of the intermediates in the process of degenerate chain branching. These reactions are also catalyzed by transition metal ions. Especially well studied is the acceleration of radical decomposition of intermediately formed hydroperoxides (see, e.g., [10]). 

Finally, the CH2OH radicals react with O2 to give HCHO and HO2 (5.327). Thus, C2 is broken down into Ci species. Fig. 5.34 shows schematically the C2 gas phase chemistry. It is obvious that there is no ethanol formation and acetic acid decomposition, whereas acetaldehyde provides many pathways back to Ci chemistry. Glycolaldehyde is a highly water-soluble product from several C2 species (ethene, acetaldehyde and ethanol) other bicarbonyls, however, are likely to be produced preferably in solution. The aqueous phase produces other C2 speeies but also deeomposes them (Fig. 5.35). By contrast, in aqueous solution from Ci, C2 species can be given as shown by the formation of glyoxal from the formyl radicals (5.351) the latter is... 

The known free-radical decomposition of aryl nitrosoamides (ArN(NO)COR ) and the report that nitrosoamides of 0-alkyl-hydroxylamines decompose by a free-radical pathway indicate that free-radical processes might occur in the normal nitrosoamide decomposition. In fact, the aliphatic nitrosoamides have been used as initiators at elevated temperatures for the polymerization of styrene and other olefins At, or near, room temperature, however, it appears that free radicals are not formed in the nitrosoamide decomposition. It has been found, for example, that (1) COj (a product of the decarboxylation of carboxyl radicals) is not formed in the decomposition (2) the scavenger nitric oxide has no effect on the reaction (3) normal products and no polymer are formed in the decomposition of A -(i-butyl)-A -nitrosobenzamide ° ° and N-nitroso-7V-(l-phenylethyl)acetamide -in styrene and (4) no difference in acetate yields is observed when A -nitroso-A-(1-phenyl-ethyl) acetamide is decomposed in benzene in the presence or absence of 0-1 m Styrene and 1-phenylethyl acetate react with... 

When the decomposition is carried out in an inert solvent, methyl acetate and ethane are formed, whereas in the gas-phase decomposition methyl acetate is completely absent and ethane is produced in much smaller quantity, It was suggested that the dimers in solution represent the recombination of methyl, and the combination of methyl and acetoxy radicals, within the solvent cage. ... 

Free-radical carboxymethylation of several aromatic compounds has been reported, " the -CHaCOOH radical being produced by the thermal decomposition of benzoyl peroxide in acetic acid. More recently the carboxymethylation of dibenzofuran brought about by the thermal decomposition of chloroacetylpolyglycolic acid (41) has... 

Den Hertog and Overhoff - observed that when pyridine in sulfuric acid is added to molten potassium sodium nitrate the 3-nitro derivative is formed at 300°C, whereas at 450°C 2-nitropyridme is the main product. The latter is probably a free-radical process. Schorigin and Toptschiew obtained 7-nitroquinoline by the action of nitrogen peroxide on quinoline at 100°C, possibly through the homolytic addition of NOa. Laville and Waters reported that during the decomposition of pernitrous acid in aqueous acetic acid, quinoline is nitrated in the 6- and 7-positions. They considered that the reaction proceeds as shown in Scheme 3. 

MAIs may also be formed free radically when all azo sites are identical and have, therefore, the same reactivity. In this case the reaction with monomer A will be interrupted prior to the complete decomposition of all azo groups. So, Dicke and Heitz [49] partially decomposed poly(azoester)s in the presence of acrylamide. The reaction time was adjusted to a 37% decomposition of the azo groups. Surface active MAIs (M, > 10 ) consisting of hydrophobic poly(azoester) and hydrophilic poly(acrylamide) blocks were obtained (see Scheme 22) These were used for emulsion polymerization of vinyl acetate—in the polymerization they act simultaneously as emulsifiers (surface activity) and initiators (azo groups). Thus, a ternary block copolymer was synthesized fairly elegantly. 

From a study of the decompositions of several rhodium(II) carboxylates, Kitchen and Bear [1111] conclude that in alkanoates (e.g. acetates) the a-carbon—H bond is weakest and that, on reaction, this proton is transferred to an oxygen atom of another carboxylate group. Reduction of the metal ion is followed by decomposition of the a-lactone to CO and an aldehyde which, in turn, can further reduce metal ions and also protonate two carboxyl groups. Thus reaction yields the metal and an acid as products. In aromatic carboxylates (e.g. benzoates), the bond between the carboxyl group and the aromatic ring is the weakest. The phenyl radical formed on rupture of this linkage is capable of proton abstraction from water so that no acid product is given and the solid product is an oxide. 

Although Ce(IV) oxidation of carboxylic acids is slow and incomplete under similar reaction conditions , the rate is greatly enhanced on addition of perchloric acid. No kinetics were obtained but product analysis of the oxidations of -butyric, isobutyric, pivalic and acetic acids indicates an identical oxidative decarboxylation to take place. Photochemical decomposition of Ce(IV) carbo-xylates is highly efficient unity) and Cu(ll) diverts the course of reaction in the same way as in the thermal oxidation by Co(IIl). Direct spectroscopic evidence for the intermediate formation of alkyl radicals was obtained by Greatorex and Kemp ° who photoirradiated several Ce(IV) carboxylates in a degassed perchloric acid glass at 77 °K in the cavity of an electron spin resonance spectro-... 

The back recombination of the pair of acetoxyl radicals with the formation of parent diacetyl peroxide was observed in special experiments on the decomposition of acetyl peroxide labelled by the lsO isotope on the carbonyl group [78,79]. The reaction of acetyl peroxide with NaOCH3 produces methyl acetate and all lsO isotopes are contained in the carbonyl... 

The decomposition of both the chloride and acetate hydride is halted by a phenolic inhibitor, indicating a radical mechanism, but the details are not clear.436 BuSnCl2H, which is believed to be formed when BuSnH3 and BuSnCl3 are mixed, is similarly unstable.437... 

There have been examples of sonochemical switching in homogeneous reactions. The decomposition of lead tetraacetate in acetic acid in the presence of styrene at 50 °C generates a small quantity of diacetate via an ionic mechanism. Under otherwise identical conditions sonication of the mixture gives 1-phenylpropyl acetate predominantly through an intermediate methyl radical which adds to the double bond (Scheme 3.8) [55,56]. These results are in accord with the proposition that radical processes are favoured by sonication. 

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