Alkyl formates, radical

When )3-scission can occur in the radical, further reactions compete with acid amide formation. Thus oxaziridine (112) with iron(II) ion and acid yields stabilization products of the isopropyl radical. If a-hydrogen is present in the Af-alkyl group, radical attack on this position in (113) occurs additionally according to the pattern of liquid phase decomposition. 

This is clo.sely related to the Tertiary radical synthesis" scheme for the preparation of organocobalt porphyrins, in which alkenes insert into the Co—H bond of Co(Por)H instead of creating a new radical as in Eq. (13). If the alkene would form a tertiary cobalt alkyl then polymerization rather than cobalt-alkyl formation is observed. " " " The kinetics for this process have been investigated in detail, in part by competition studies involving two different alkenes. This mimics the chain transfer catalysis process, where two alkenes (monomer and oligomers or... 

Useful sources of these radicals were the hydrogen abstraction from alkyl formate and especially the decomposition by ferrous salts of mixtures of hydrogen peroxide and a-keto esters. The alkoxy-carbonyl radicals appear to be less nucleophilic than carbamoyl radicals. 

A high-level ab initio study of related reactions of alkyl nitrates (RO—NO2) at the G3 and B3LYP/6-311-I— -G(d,p) levels has revisited the reactions of alkyl peroxy radicals (ROO") with nitric oxide. Activation barriers for the isomerization of RO—ONO to RO—NO2 were found to be too high to account for the formation of alkyl nitrates... 

Some homolytic fragmentation reactions are driven by formation of small, stable molecules. Alkyl acyloxyl radicals (RCOp decarboxylate rapidly (fe > 1 x 10 s ) to give alkyl radicals, and even aryl acyloxyl radicals (ArCOp decarboxylate to aryl radicals with rate constants in the 10 s range." Azo radicals produced in the homolysis of azo initiators eliminate nitrogen rapidly. Elimination of carbon monoxide from acyl radicals occurs but is slow enough (fe 10" -10 such that the acyl radical can be trapped in a bimolecular process,... 

Most of the other products found in irradiated meat volatiles except those containing sulfur or aromatic rings may also be accounted for by mechanisms associated with alkyl free radical formation in the fat. Oxygenated compounds are far less abundant than hydrocarbons, but appreciable amounts of a homologous series of n-aliphatic alcohols up to hexanol are found. Of these, only ethanol is detected in the unirradiated controls. Since the water content of meat averages nearly 60%, the formation of alcohols may be thought to occur by reaction of the alkyl free radical with water. Such a mechanism is supported by the fact that only traces of alcohols are found in irradiated dry butterfat and were undetected in irradiated triglycerides or methyl esters of fatty acids. 

Alfassi ZB, Mosseri S, Neta P (1987) Halogenated alkyl peroxyl radicals as oxidants effects of solvents and of substituents on rates of electron transfer. J Phys Chem 91 -.3383-3385 Alfassi ZB, Marguet S, Neta P (1994) Formation and reactivity of phenyl peroxyl radicals in aqueous solutions. J Phys Chem 98 8019-8023... 

Bauer G (2000) Reactive oxygen and nitrogen species efficient, selective and interactive signals during intercellular induction of apoptosis. Anticancer Res 20 4115-4140 Beckwith AU, Davies AG, Davison IGE, Maccoll A, Mruzek MH (1989) The mechanisms of the rearrangements of allylic hydroperoxides 5a-hydroperoxy-3p-hydrocholest-6-ene and 7a-hydro-peroxy-3(1-hydroxycholest-5-ene. J Chem Soc Perkin Trans 2 815-824 Behar D, Czapski G, Rabani J, Dorfman LM, Schwarz HA (1970) The acid dissociation constant and decay kinetics of the perhydroxyl radical. J Phys Chem 74 3209-3213 Benjan EV, Font-Sanchis E, Scaiano JC (2001) Lactone-derived carbon-centered radicals formation and reactivity with oxygen. Org Lett 3 4059-4062 Bennett JE, Summers R (1974) Product studies of the mutual termination reactions of sec- alkylper-oxy radicals Evidence for non-cyclic termination. Can J Chem 52 1377-1379 Bennett JE, Brown DM, Mile B (1970) Studies by electron spin resonance of the reactions of alkyl-peroxy radicals, part 2. Equilibrium between alkylperoxy radicals and tetroxide molecules. Trans Faraday Soc 66 397-405... 

Thermolytic Reactions. At the higher temperatures, nonoxidative reactions also occur as for example the formation of tetrasubstituted cyclohexenes via Diels-Alder reaction, or the formation of dehydrodimers and mono- or polycyclic dimers via combination of alkyl free radicals or free radical attack on double bonds. 

This was an attempt at a crossover experiment, possibly relevant to the mechanism of photolysis, Eqs. (8)—(11) a trace of Sn(NR )3 was also present, but not detected with 1 1 SnR2 Sn(NR2)2, nor any mixed alkyl-amido-radical (142). Irradiation of Sn(NRj)2 with Sn(C5H5-i))2 yielded Sn(NR2)(C5H5-i7), but no paramagnetic species. Radical formation was also not detected by UV irradiation of Sn(C5H6-7))j, Snl2, SnCI(NR ), or Zn(NR )2. 

In the atmosphere the nitrooxy alkyl peroxy radical, > C(0N02) - COO( ) <, behaves like other alkyl peroxy radicals and will react with NO2, HO2, and other peroxy radicals. Reaction of nitrooxy alkyl peroxy radical with NO is unlikely because the conditions necessary for the formation of NO3 radicals (high O3) are incompatible with the presence of significant amounts of NO. For unsymmetrical alkenes the addition of NO3 radicals leads to the formation of two different peroxy radicals, e.g., for propene ... 

Incorporation of triethylamine into the reaction medium produced more reduction product presumably due to electron transfer from the triethylamine to the excited alkyl halide. This results in a weakly-bound amine-alkyl halide pair [57]. The alkyl halide radical anion releases X- (Scheme 17). In a related example, it is known that solutions of aliphatic amines in CC14 are unstable to light quickly forming white crystalline precipitates [60]. The initial reaction is formation of a singlet radical pair via excitation of a ground state charge-transfer complex. 

Although the stability of the tetroxide molecules is very low at ambient temperatures it seems likely that the irreversible decay of alkyl peroxy-radicals does proceed through the formation of a tetroxide molecule which can then either decompose reversibly into the alkyl peroxy-radicals or decompose irreversibly into non-radical products. 

Its subsequent reactions with O3, CO, and other VOCs, in the presence of nitrogen oxides (NOj ) lead to the formation of HO2, hydrogen peroxide, alkyl peroxy radicals, and ultimately to the production of ozone via the conversion of NO2 to NO [8,21],... 

The reactions of the OH radicals with two model thioether compounds, S-ethylthioacetate (SETAc) (H3C-CH2-S-C(=0)-CH3) and S-ethylthioacetone (SETA) (H3C-CH2-S-CH2-C(=0)-CH3, containing electron withdrawing acetyl groups in the a and f3 positions, with respect to the sulfur atom have been studied by pulse radiolysis. The a-positioned acetyl group in SETAc destabilizes >S -OH radicals within the five-membered structure that leads to the formation of alkyl-substituted radicals H2C -CH2-S-C(=0)-CH3 and H3C-CH2-S-C(-0)- CH2. At high proton and SETAc concentration, the OH-induced oxidation does not lead to intermolecularly three-electron-bonded dimeric radical cations SETAc(S.. S), only the a-(alkylthio)alkyl radicals H3C- CH-S-C(=0)-CH3 were observed (Amax = 420 nm). These observations are rationalized in terms of the... 

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