Secondary disproportionation

Assumes double-bond isomerization, but no secondary disproportionation reactions. Ref. I6>... 

It has already been noted that the esters of arsinous and arsonous acids disproportionate of heating. The formation of As(OR)3 in the pyrolysis of arsonic acid derivatives is thought to be the product of the secondary disproportionation reaction of the primary product RAs(OR)2-... 

Microscopic investigations of the germanium powder samples after washing out the salt components from the cathode deposit reveal two different kinds of crystals large germanium dendrites and very fine particles. According to the above mechanism, the first can be considered as a primary electrocrystallization product, while the second is a product of a secondary disproportionation of film s LVI. 

Although primary and secondary alkyl hydroperoxides are attacked by free radicals, as in equations 8 and 9, such reactions are not chain scission reactions since the alkylperoxy radicals terminate by disproportionation without forming the new radicals needed to continue the chain (53). Overall decomposition rates are faster than the tme first-order rates if radical-induced decompositions are not suppressed. 

A secondary competing reaction can occur where chlorine dioxide disproportionates in the alkaline solution, producing sodium chlorite and chlorate ... 

The most efficient intramolecular secondary processes competing with the acyl-alkyl diradical recombination in five-membered and larger cyclic ketones are hydrogen shifts resulting in the disproportionation of the diradical to either ketenes or unsaturated aldehydes [cf. (5) (4) (6)]. 

The allylic-type furylic radical 6 is resonance stabilized to such a degree that its reactivity in promoting propagation by adding onto another furan ring is minimal. The fate of these radicals will simply be to couple with another radical present in the reaction medium (primary or secondary) or to disproportionate to regenerate the furan character of the ring26. ... 

For /-butyl peresters there is also a variation in efficiency in the series where R is primary secondary>tertiary. The efficiency of /-butyl peroxypentanoate in initiating high pressure ethylene polymerization is >90%, that of /-butyl peroxy-2-ethylhexanoate ca 60% and that of/-butyl peroxypivalate ca 40%.196 Inefficiency is due to cage reaction and the main cage process in the case where R is secondary or tertiary is disproportionation with /-butoxy radicals to form /-butanol and an olefin.196... 

The possibility of predicting solid state reactivity from calculated thermochemical data was first addressed with ketodiesters 65a-e, which were substituted with methyl groups to vary the extent of the RSE in the radicals 65-BRl - 65-BR3 involved along the photodecarbonylation pathway (Scheme 7.19). " All ketones reacted in solution to give complex product mixtures from radical combination (66a-e) and disproportionation processes. Calculations revealed RSEs of 8.9 kcal/mol, 15.1 kcal/mol, and 19.8 kcal/mol for radicals 65-BRl (primary enol radical), 65-BR2 (secondary enol radical), and 65-BR3 (tertiary enol radical), respectively. In the... 

RA alone leads to changes in cellular immunity and causes a disproportionate increase in pulmonary infection and sepsis.11 Because medications that alter the immune system are linked to an increased risk of infection, it is difficult to distinguish between an increased risk of infection secondary to RA and the medications used to treat RA. Patients and clinicians must pay close attention to signs and symptoms of infection because of this increased risk.11... 

Scheme 5 The Russel scheme of secondary peroxyl radical disproportionation.

The most probable elementary step from which chemiluminescence is emitted is disproportionation of secondary peroxyl radicals, which may be formed only on carbon 6 of the glucopyranosyl unit. According to various authors, who accept the Russel Scheme 5 of disproportionation of secondary peroxyl radicals as a possibility leading to the light emission, it may be deduced that carboxylic acid,... 

Russell proposed the mechanism of disproportionation of primary and secondary peroxyl radicals 2R1R2C1IOO —> R1 R2C(0) + o2 + r r2choh G. A. Russell [68]... 

Chemiluminescence in the liquid-phase hydrocarbon oxidation was discovered. It was proved to be the result of secondary peroxyl radicals disproportionation R. F. Vasi ev, O. N. Karpukhin, and V. Ya Shlyapintokh [69]... 

A very serious problem was to clear up the formation of hydroperoxides as the primary product of the oxidation of a linear aliphatic hydrocarbon. Paraffins can be oxidized by dioxygen at an elevated temperature (more than 400 K). In addition, the formed secondary hydroperoxides are easily decomposed. As a result, the products of hydroperoxide decomposition are formed at low conversion of hydrocarbon. The question of the role of hydroperoxide among the products of hydrocarbon oxidation has been specially studied on the basis of decane oxidation [82]. The kinetics of the formation of hydroperoxide and other products of oxidation in oxidized decane at 413 K was studied. In addition, the kinetics of hydroperoxide decomposition in the oxidized decane was also studied. The comparison of the rates of hydroperoxide decomposition and formation other products (alcohol, ketones, and acids) proved that practically all these products were formed due to hydroperoxide decomposition. Small amounts of alcohols and ketones were found to be formed in parallel with ROOH. Their formation was explained on the basis of the disproportionation of peroxide radicals in parallel with the reaction R02 + RH. 

It can be seen that primary and secondary R02 radicals disproportionate with the participation of the a-C—H bond. This explains why the substitution of D in the a-position for H retards the recombination of R02 [/tn//tD =1.9 for ethylbenzene, h/ d = 2.1 for styrene, and h/ d=1-37 for diphenylmethane [179]). Because of this, R02 radicals of unsaturated compounds with a double bond in the a-position to the peroxyl free valence disproportionate more rapidly than structurally analogous aliphatic peroxyl radicals (at 300 K, 2kt = 2x 107 and 3.8 x 106 L mol-1 s-1 for R02 radicals of cyclohexene and cyclohexane, respectively [180]). Among the products of secondary peroxyl radicals disproportionation, carbonyl compound and alcohol were found in a ratio of 1 1 at room temperature (in experiments with ethylbenzene [181], tetralin [103], and cyclohexane [182-184],... 

Hydrogen peroxide was identified as the product of secondary peroxyl radical disproportionation [187-192], It cannot be explained by the concerted mechanism of tetroxide decomposition. 

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