Radical chain decomposition

The key step in the radical chain decomposition of alkanesulfonyl halides as well as in the adduct formation of sulfonyl halides with alkenes (vide infra) is equation 8 in which the R radical abstracts an X atom from the sulfonyl halide to regenerate a sulfonyl radical. 

Finally, I identified another factor, a variable air leak. When I eliminated this, both dichloroethanes decomposed slowly by the unimolecular mechanism. When I let in a controlled flow of air (or chlorine), the 1,2-dichloroethane (in contrast to the 1,1-isomer) now decomposed rapidly at a much lower temperature. I had discovered my first new reaction the radical chain decomposition of the dichloride as in Scheme 2. 

Berlin, A. (1986). Kinetics of radical-chain decomposition of persulfate in aqueous solutions of organic compounds. Kinetic Catal. 27,34-39. 

One of the best-known examples of a radical-chain decomposition is the gas-phase pyrolysis of 1,2-dichoroethane to vinyl chloride and hydrogen chloride... 

Many unsaturated chloro- and bromo-hydrocarbons and many polychloro and polybromo compounds decompose by radical-chain mechanisms, but only the chloro compounds have been studied in reasonable detail, presumably owing to the complex nature of the chain reactions in the case of the bromo compounds. Other examples of compounds which undergo radical-chain decompositions are 2,2-dichlorodiethyl ether oxalyl chloride alkyl hypochlorites alkyl peroxychloroformates and alkyl chloro-sulphites in the gas phase ... 

Yates and Hughes photochemically stimulated the radical-chain decomposition of 1,2-dichloroethane to vinyl chloride and hydrogen chloride. They obtained an overall activation energy of 12.5 kcal.mole from which they deduced an activation energy of 23.0 kcal.mole" for the step... 

D(C1-C02R) = 56 kcal.mole" would satisfy the observed kinetics. This value (which seems too low by about 5-lOkcal.mole" ) is certainly a lower limit because surface initiation reactions are undoubtedly also important. The Arrhenius /4-factors observed for the normal elimination reactions to olefin, HCl, and CO2 fluctuate around the transition state estimates and do so probably as a result of experimental errors and reaction complexities. Note that the chloroformic acid, which is the primary elimination product, is very unstable at reaction temperatures and rapidly decomposes, probably by a 4-center transition state, to give HCl -I- CO2 (ref. 159). The experimental reaction rates of the chloroformate ester eliminations are two powers of ten faster than those for the corresponding formate and acetate esters. This is reasonable since electron withdrawing substituents at the (C-1) position accelerate the decompositions. It seems likely, then, that the normal uni-molecular eliminations and the free radical chain decompositions are competitive processes in these chloroformate ester reactions. 

Corey, E. J., Hertler, W. R. A study of the formation of halo amines and cyclic amines by the free radical chain decomposition of N-haloammonium ions (Hofmann-Lbffler reaction). J. Am. Chem. Soc. 1960, 82,1657-1668. 

The major part of the reactions of a-arylation which have been reported were performed on substrates containing active methylene groups, such as p-diketones, p-ketoesters, P-ketonitriles and malonic acid derivatives. Less activated compounds, such as P-ketosulfides have also been efficiently arylated on the a-carbon. (Table 5.3) The yield of the arylated product can be increased by addition of 1,1-diphenylethylene, acting as a free radical trap. For example, in the reaction of phenylation of ethyl cyclohexanonecarboxylate, addition of 1,1-diphenylethylene reduced the radical chain decomposition in such a way that an 80% yield was obtained instead of 55% in absence of 1,1-diphenylethylene. ... 

Adam, W., R. Curci, M.E. Gonzalez Nunez, and R. Mello (1991). Thermally and photochemically initiated radical chain decomposition of ketone-free methyl(trifluoromethyl)dioxirane. J. Am. Chem. Soc. 113, 7654-7658. 

In the free-radical chain decomposition of peracids [reactions (1)— 4)] the stereo-... 

The several chain reaction sequences propagated by methyl radicals follow a common pattern, with initiation by abstraction or addition, and propagation by radical decomposition, but there are notable differences. Thus with ethane, only abstraction is possible, but with ethylene both abstraction and addition sequences occur with acetylene the abstraction sequence is blocked by the stability of the CoH radical so that only addition is important, while with propylene, abstraction of the allylic hydrogen is apparently much faster than addition, and the former predominates. Finally, it should be noted that initially there is no radical-chain decomposition of methane further, that the chain sequences initiated by abstraction do not consume methane, and only with the addition sequences, beginning with ethylene, is methane consumed even then it is a limited chain, limited by the amount of olefin present. 

General. The free radical chain decomposition of halogen (mainly chlorine) substituted methanes (XM) and haloethanes (XEtY), was studied in cyclohexane. The propagation step of the chain reaction of halomethanes is given by reactions 32 and 33 while reactions 34 through 37 describe the chain decomposition of haloethanes. These reactions can be... 

In an attempt to get a more basic understanding of the initiator system, we undertook a study of the kinetics of de -composition of aqueous potassium persulfate.In O.lN potassium hydroxide buffer, the apparent activation energy for decomposition was found to decrease from 33.5 kcal/mole to 19.9 kcal/mole upon the addition of 18-crown-6. A more detailed investigation has now shown this to be a radical chain decomposition in which crown is being oxidized. The accelerated decomposition seems to be due to the reaction of the crown cation radical and persulfate dianion (Scheme 2). Addition of a free radical trap, in this case methacrylonitrile, suppressed the rate of persulfate disappearance to that normally observed in the absence of crown. 

Q, tn er eine neue bildungsweise von N-alkylierten Pyrrolidin, Ber., 42, 3427,1909 (c) Corey, E.J. and Hertler, W.R., A study of the formation of haloamine and cyclic amines by the free radical chain decomposition of N-haloammonium ions (Hofmann-Loffler reaction), /. Am. Chem. Soc., 82, 1657, I960. (d) Wolff, M.E., Cyclization of N-halogenated amines (The Hofmann-Loffler reaction), Chem. Rev., 63, 55, 1963. 

Gilbert KE, Gajewski JJ. Coal liquefaction model studies free radical chain decomposition of diphenylpropane, dibenzyl ether, and phenyl ether via P-scission.J Org Chem. 1982 47 4899-4902. 

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