Malonic acid radical

The free-radical scheme, however, fails to account for the following (i) It cannot be easily generalised to cover the identical kinetics of the Mn(lII) sulphate oxidation if -CH(C02H) has an oxidation potential comparable with Mn(Ill)/ Mn(II) pyrophosphate then it cannot appreciably reoxidise Mn(ll) sulphate, (a) If -CH(C02H) reoxidises Mn(II) sulphate then it should be capable of re-oxidising both V(1V) sulphate (of the V(V)/V(IV) pair, potential 1.0 V) and Mn(II) sulphate in the V(V) oxidation of malonic acid that it does neither can be seen from the rate laws of these oxidations which show no Mn(II)-retardation vide infra). Hi) The not dissimilar kinetics of the Mn(III) sulphate oxidation of formic acid vide supra) and mercurous ion °. 

There are also reactions in which electrophilic radicals react with relatively nucleophilic alkenes. These reactions are exemplified by a group of procedures in which a radical intermediate is formed by oxidation of readily enolizable compounds. This reaction was initially developed for /3-ketoacids,311 and the method has been extended to jS-diketones, malonic acids, and cyanoacetic acid.312 The radicals formed by the addition step are rapidly oxidized to cations, which give rise to the final product by intramolecular capture of a carboxylate group. 

The carbamates 327 (R R2 Pr or Bu) react with t-butylthiol, malonic acid and ethoxyethylene under irradiation to yield the (ethoxyethyl)amines 333 via the radical cations 332. The A-allyl analogues 334 (R = Pr or PhCH2) cyclize to pyrrolidines 335382. 

Hydroxy-4-methylthiazole-2(3//)thione carbamates, e.g. the cyclohexyl derivative 336, are precursors for monoalkylaminium cation radicals, which cannot be prepared from 2-thioxopyridinyloxycarbamates. The carbamate is obtained from 3-hydroxy-4-methylthiazole-2(3//)-thione and cyclohexyl isocyanate. When irradiated in the presence of malonic acid and /-butyl hydrogen sulphide it yields the cyclohexylaminium cation... 

Three C60 derivatives with two to four malonic acid groups (DMA C60, TMA C60, and QMA C60) were prepared and the phototoxicity of these compounds against HeLa cells was determined by MTT assay and cell cycle analysis (Yang et al., 2002). The relative phototoxicity of these compounds was DMA C60 > TMA C60 > QMA C60. Hydroxyl radical quencher mannitol (lOmM) was not able to prevent cells from the damage induced by irradiated DMA C60. DMA C60, together with irradiation, was found to decrease the number of G(l) cells from 63% to 42% and increase G(2) + M cells from 6% to 26%. 

Cheng F, Yang X, Zhu H et al. (2000) Synthesis of oligoadducts of malonic acid C60 and their scavenging effects on hydroxyl radical. J Phys Chem Solids. 61 1145-1148. 

When 151 is caused to react with terf-butyl chloride, a coupling occurs in high yield [Eq. (99)] the substitution seems neither to be an SN1 nor an SN2 reaction but was suggested to occur via an initial electron transfer from 151 to f-BuCl, followed by coupling of the two radicals [Eq. (99)].37 Anion 151 also reacts with carbon dioxide, forming a spiro derivative of malonic acid. 

A series of low-temperature reactions in condensed media has been studied by Dubinskaya et al. (see the references cited in ref. 76). For example, the reaction rate constants for H atom transfer from malonic acid and acetonitrile to the radicals of polyvinyl acetate have been measured [76], The activation energy of these reactions has been found to decrease with decreasing temperature and to become practically equal to zero at T < 77 K. 

The allyl radical (Figure 18.6) has been the subject of very many studies. It has been prepared in the liquid phase by electron irradiation of cyclopropane. The sign of the CH proton coupling constant was deduced by comparison with a single-crystal study of the radical CH(COOH)2 formed by y-irradiation of a single crystal of malonic acid. A straightforward UHF calculation gives a wavefunction... 

Schuchmann MN, Rao R, Hauser M, Muller SC, von Sonntag C (2000) The reaction of the malonic acid derived radical with oxygen. A reinvestigation by pulse radiolysis. J Chem Soc Perkin Trans 2 941-943... 

In peroxyl radical reactions the formation of carbonyl functions generally dominates over a reduction (Chap. 8). This would lead to the formation malonic acid aldehyde [reactions (34) and (35)]. Being an aldehyde, it should be very easy to detect (Lipari and Swarin 1982), but the corresponding experiments seem not yet to have been carried out. 

The uncatalysed Belousov-Zhabotinsky (B-Z) reaction between malonic acid and acid bromate proceeds by two parallel mechanisms. In one reaction channel the first molecular products are glyoxalic acid and carbon dioxide, whereas in the other channel mesoxalic acid is the first molecular intermediate. The initial reaction for both pathways, for which mechanisms have been suggested, showed first-order dependence on malonic acid and bromate ion.166 The dependence of the maximal rate of the oxidation of hemin with acid bromate has the form v = [hemin]0-8 [Br03 ] [H+]12. Bromate radical, Br02, rather than elemental bromine, is said to play the crucial role. A mechanism has been suggested taking into account the bromate chemistry in B-Z reactions and appropriate steps for hemin. Based on the proposed mechanism, model calculations have been carried out. The results of computation agree with the main experimental features of the reaction.167... 

The benzylic free radical produced by the addition of the carbamoyl radical to the ethyl cinnamate molecule is more stable than the alternative radical alpha to the ester group. With such an orientation of addition to the a,p-unsaturated ester, this reaction should lead to derivatives of malonic acid. However, it has been found that the intermediate radical, being a stable benzylic free radical, fails to perform the subsequent abstraction of a hydrogen atom from formamide, and thus no chain-transfer step takes place. Instead of performing this step it favours the combination with a semi-pinacol radical, which is present in solution, to yield the hydroxy ester which subsequently lactonizes to give the major product of the reaction (67). 

Radiolytic e.s.r. studies of the reactions of SO4, Cl2, and Brf radicals with organic compounds are currently being carried out in this laboratory by Fessenden et al. One of the interesting findings is the selective decarboxylation by SO4 radicals of certain aliphatic and aromatic carboxylic acids, whereas earlier studies with OH had shown that decarboxylation is not important in such cases. For example, it has been reported that the reaction of OH with malonic acid results mainly in hydrogen abstraction, with only 10% decarboxylation in acid solution and <0-5% in alkaline solution (Behar et al., 1973). 

Wang used reactive-extrusion polymerization with 2,5-di-methyl-2,5-di-t-bu-tylperoxy hexane to prepared a graft copolymer, (11), by free radically grafting polyethylene-glycol malonic acid onto the biodegradable substrate of poly((3-hydroxybutyrate-co- p-hydroxy valerate). 

In flavonoids acylated with aliphatic acids, the most common acids are acetic and malonic. In the MS fragmentation of the dicarboxylic acids (as malonic acid), a first loss of 44 mass units is observed (loss of the carboxylic radical, CO2), and this is due to decarboxylation. 

In the case of malonic acid and other compounds when the methylene group is linked to two carboxyl groups the sodium compounds are more easily formed than are the sodium compounds of the alkyl radicals themselves. These sodium compounds of malonic acid ester, are especially reactive toward alkyl halides with the result that the alkyl radical is introduced into the malonic acid ester in place of the sodium, i.e.y in place of hydrogen of the methylene group. This is shown by the following reactions. 

The homologues of succinic acid are analogous to those of malonic acid and are formed by the introduction of alkyl radicals into the carbon groups that are not carboxyl in character. As succinic acid contains two such carbon groups, each of which has two replaceable hydrogens, we may have the introduction of one, two, three or four alkyl radicals. Taking, as an illustration, the methyl substitution products of succinic acid we may have the following compounds ... 

The heterocoupling of carboxylic acids bearing chiral auxiliaries has been used to study the diastereoselectivity of the coupling of Kolbe radicals [204b]. For that purpose, 2-substituted malonic acid amides bound to seven different chiral auxiliaries were coelectrolyzed with different coacids [Eq. (200]- The yields in heterodimer ranged between 13 to 69%, and the diastereoselectivities between 20 and 86% de. 

Acetic acid gives the methyl radical as well as CHg. COgH, and malonic acid gives only 0112.00211. These decarboxylation products possibly arise from abstraction of carboxylic hydrogen followed by, or concerted with, decarboxylation of the acyloxy radical, e.g. 

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