Ethyl radicals, scavenging

Kinetics of the reaction of p-nitrochlorobenzene with the sodium enolate of ethyl cyanoacetate are consistent with this mechanism. Also, radical scavengers have no effect on the reaction, contrary to what would be expected for a chain mechanism in which aryl radicals would need to encounter the enolate in a propagation step. The reactant, /i-nitrophenyl chloride, however, is one which might also react by the addition-elimination mechanism, and the postulated mechanism is essentially the stepwise electron-transfer version of this mechanism. The issue then becomes the question of whether the postulated radical pair is a distinct intermediate. 

Two of the many products of ethylene radiolysis—methane and propane—show no or only negligible variation with field strength. Methane is produced by a molecular elimination process, as evidenced by the inability of oxygen or nitric oxide to quench its formation even when these additives are present in 65 mole % concentration (34). Propane is completely eliminated by trace amounts of the above scavengers, suggesting methyl and ethyl radicals as precursors ... 

The vinyl radical concentration was only 2-3 % of the ethyl radical concentration but was unaffected by the addition of deuteroethylene as scavenger. It seems likely that it arises as a primary product of the radiolysis, viz. 

The most conclusive evidence that the larger yield of ethylene from s-butylcyclopropane is not due to the ethyl radicals is that the difference still exists in the presence of scavenger radicals as O2. In the presence of oxygen the yield of ethylene is G = 0.30, 0.20,1.00, and 0.53 for n-butyl, isobutyl, s-butyl and t-butyl, respectively. 

A feature of the radiolysis experiments which requires some additional clarification concerns the ethylene product. One might object to the omission of any contribution from radical reactions to the ethylene product since radical scavengers affect the yield of this unsaturate. Thus, oxygen sharply reduces the ethylene product while nitric oxide has a less pronounced effect. However, since both scavengers have identical effects on all the rest of the products in the system, we are inclined to interpret the reduction of ethylene in the presence of these additives to quenching of the excited state of the ethyl chloride molecule which eliminates HC1. It has been supposed for some time that oxygen efficiently quenches certain excited states hence, this suggestion does not seem unreasonable. 

Beilstein Handbrjok Reference) AI3-28026 BRN 1731349 CCRIS 964 Diethylhydroxyl-amine N,N-Diethylhydroxyamine EINECS 223-055-4 Ethanamine, N-ethyl-N-hydroxy- Hydroxylamine, N,N-diethyl- N-Hydroxydiethylamine Pennstop 1866. Free radical scavenger used by the rubber industry as an emulsion polymerization inhibitor vapor phase inhibitor for olefin or styrene monomer recovery systems in-process inhibitor for production of styrene, divinyl benzene, butadiene and isoprene. Liquid mp = 10° bp = 133° d = 0.8669. ElfAtochem N. Am. 

To account for the rapid increase of quantum yields up to methanol concentrations of 5 X 10 M, it was supposed that reaction (4) becomes increasingly predominant at the expense of the recombination reaction, which is the reverse of reaction (2). The slower increase at higher concentrations may arise as a continuation of this effect, or, since the methanol absorption becomes appreciable, hydrogen may be formed by direct photolysis of methanol, with a higher quantum yield than for water. Experiments using ethyl acetate as a radical scavenger indicate that the quantum yield for the production of hydrogen from water ((pw) is 0.64, which compares favorably with the value from the methanol system (pw, 0.6). 

This type of cleavage was supported by CIDNF experiments and by the use of diamagnetic radical scavengers as spin traps for the radicals produced during the photolysis of benzoin and benzoin methyl ether (32). In both cases CgH CO and CgH CHOR (R=H,CH3) radicals were trapped and characterized from the ESR spectra of the stable nltroxlde radicals. Heine (33,34) Isolated the products formed on photolysis of benzoin alkyl ethers (methyl, ethyl, isopropyl) in benzene these were also indicative of the intermediacy of benzoyl and alkoxybenzyl radicals as shown in the following scheme ... 

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